For decades, the Tower 18 junction at Lake & Wells was billed as the busiest railroad junction in the world. The towerman certainly had a lot on his hands in this photo looking north from the transfer bridge at the adjacent Randolph/Wells station: A 4000-series Baldie turns south (right front) on its way back to Logan Square via the Met main line and a southbound Englewood Express of wooden cars flies through (left), while a crosstown train of South Side cars, one of which is designated as a Smoker (below the American flag on the tower) turns north onto Wells. For a larger view, click here. (Photo from the Chicago Transit Authority Collection)

Tower 18
Wells Street and Lake Street, Loop

Service Notes:


Green Line: Lake-Ashland-East 63rd

Brown Line: Ravenswood

Orange Line: Midway

Purple Line: Evanston Express

Pink Line: 54/Cermak-Loop

Quick Facts:

Established: October 3, 1897
Original Line: Union Elevated Railroad
Rebuilt: 1969
Status: In Use


This view looks north on Fifth Avenue (Wells Street) at Tower 18 from Randolph. The Randolph & Wells station can be seen in the bottom of the photo. Note also the cables leading from the signal in the lower right, between the tracks, to the tower, where hand-throw levers controlled the semaphore readings. For a larger view, click here. (Photo from the Bruce G. Moffat Collection)

The location that is now home to Junction 18 (and Tower 18) began life not as a junction but as a station. On September 22, 1895, a new section of structure was opened over Lake Street from Market to Wabash, with through trains of the Lake Street Elevated rerouted from the Market & Madison terminal to the new downtown terminal at State & Lake. Additional stations were provided at Clark and at Fifth [Wells] on the extension, which was planned to become the north leg of an as-yet-unbuilt Union Loop. In 1896, construction began on the rest of the Loop and Lake Street trains were the first to be routed on the new quadrangle when it opened on October 3, 1897. As a result of the construction, the south platform and station house of the Lake Street's Fifth Avenue station were removed to connect the west leg of the Loop (which used Fifth Avenue) to the north leg. (To compensate for the loss of the station, Randolph/Wells was actually built midway between Randolph and Lake Streets, with the station house over Couch Place, a glorified alley. An entrance to Randolph/Wells was not built at Randolph Street until 1913.) Although the north (eastbound) station house and platform at Fifth Avenue remained for the time being, Junction 18 was now established at the corner of Fifth & Lake where the Lake Street Elevated connected at the northwest corner of the Loop. There was still no Tower 18, however, as there were actually no crossovers or switches in the initial configuration.

In early 1900, the Northwestern Elevated Railroad neared completion and was to connect to the Loop at Lake & Fifth, at the same corner as the Lake Street Elevated. This required the December 17, 1899 closure and eventual removal of the eastbound platform and station house of the Fifth Avenue station (making it one of the shortest lived stations in "L" history). Tower 18 was now established.

So, why is Tower 18 called "Tower 18"? For administrative reasons that have now become unclear, the 11 stations and and three junctions on the Loop were assigned numbers beginning at the Van Buren & Fifth junction and counting up going counterclockwise around the Loop. The scheme progressed as follows:

8 - Fifth & Van Buren junction

9 - Pacific (LaSalle) & Van Buren station

10 - Dearborn & Van Buren station

11 - State & Van Buren station

12 - Van Buren & Wabash junction

13 - Adams & Wabash station

14 - Madison & Wabash station

15 - Randolph & Wabash station

16 - State & Lake station

17 - Clark & Lake station

18 - Lake & Fifth station (junction, after 1899)

19 - Randolph & Fifth station

20 - Madison & Fifth station

21 - Quincy & Fifth station

No records have survived that indicate what numbers 1-7 were to be used for, although they may have been assigned to the Union Consolidated line west of Market Street, for which the company received a franchise but had no real intention of constructing. Another theory is that they were for the various stub terminal stations and junctions, and for the Met's Franklin & Van Buren station.1 In any case, these administrative numbers survive today only in the names of the two remaining original junction towers: 12 and 18.

A northbound Northwestern Elevated train (left) passes through Tower 18 on its way north after leaving Randolph & Wells, just as a westbound Metropolitan train turn off Lake Street and into Randolph station. For a larger view, click here. (Photo from the Fred Borchert/Robert Gibson Collection)

The tower itself was a two-story affair set inside the junction between the various intersecting and diverging tracks. Its architecture was more practical than of any particular style, but did feature decorative window frames and sills, belt course moldings, and a hipped roof with a small chimney for the coal-burning stove inside. Entrance to the first floor was through a door at track level. Access to the second floor was also from outside, via a stairway on the exterior of the tower. The interior space was tight. With windows on all sides for maximum visibility, the tower was heated only by a small iron potbelly stove in the corner of the room. The junction was equipped with a hand-operated lever form of switch and signal control. This made the interior a dizzying array of levers and switches, all of which had to be precisely aligned by a vigilant towerman. In 1907, this system was retired in favor of an electro-pneumatic interlocking system that survived until the original tower's demolition. The electro-pneumatic system increased the junction's safety, for it meant that an incorrectly set switch could not result in a collision. However, the towerman was still required to make hundreds of precise routing and sequencing decisions or risk delaying the entire railroad.

Before the Loop opened, a preliminary operating plan was developed in 1895. According to The Economist, trains would circle the Loop bidirectionally using the right-hand track. Lake Street and Northwestern trains would operate in a clockwise circle using the Inner Loop, while South Side and Met trains would circle in the opposite direction on the Outer Loop. A major drawback of this plan, however, was the excessive number of conflicting movements that would occur at Tower 18. Thus, an alternate operating plan was developed, with trains operating left-handed. The pairings would remain the same, but the track assignments were swapped.

From 1900 to 1913, the track configuration of the junction remained largely the same. The Loop's left-hand running was very unusual in America, but was shared by two other "L" routes. The Northwestern Elevated was left-handed from its opening in 1900. The Lake Street was initially only left-handed for one block, between the Loop and a crossover at Franklin, at which point it resumed the right-hand running of the rest of the line. This practice remained in effect until August 7, 1902 when the railroad switched from right- to left-hand operations between Franklin and Austin to reduce switching delays and complicated Loop track assignments in preparation for the inauguration of the line's express service. The Metropolitan and South Side elevateds started as and remained right-hand railroads, making the changeover to left-hand operation upon their entrance to the Loop at Towers 8 and 12, respectively. In the initial configuration of Junction 18, the Inner Loop track, which carried the South Side and Met trains, simply curved from Lake to Wells with no switches to the other tracks. The Outer Loop track, however, held a multitude of different routing possibilities. Northwestern trains entered the Loop, turning left from Fifth onto the Outer Loop over Lake, and left the Loop northbound continuing straight ahead on the outer track over Fifth. Lake Street trains followed a similar pattern, entering by continuing straight east onto the outer track over Lake and returning to their home rails by turning west from the Outer Loop over Fifth onto the left-hand track over Lake Street. There as also an "Outer-Loop-around" track, but this was not used in any regular revenue operations.

No Lines, No Waiting: Three trains of 6000-series cars simultaneously pass through Tower 18 in the early-1950s in the only sequence possible without waiting for a train to clear. The two-car train on the left is a Ravenswood heading south into Randolph/Wells while the two-car train behind the tower is another Ravenswood turning off the Outer Loop on it way back to Kimball. The train on the right is a Douglas train, turning south into Randolph/Wells on its way back to Cicero-Berwyn Terminal. In 1954, Douglas trains would cease turning south here, instead continuing straight west through Tower 18 to access their home rails via the Lake Street Line. For a larger view, click here. (Photo from the CTA Collection)

In 1913, the Chicago Elevated Railways instituted crosstown service. With many North-South trains now through-routed, the configuration of Tower 18 would need to be changed. As part of the track realignment, the tower's electro-pneumatic interlocking system was extensively re-rigged. All Lake Street and Metropolitan trains still terminated around the Loop, as well as some night and off-peak Northwestern and South Side trains. Most North-South trains, however, went through and this required an extensive reworking of not only the Tower 18 interlocking but also Loop operating procedures. Just after midnight on November 3, 1913, all trains began operating in a counterclockwise, unidirectional manner, with Northwestern and South Side trains on the outer track and Metropolitan and Oak Park (Lake Street) trains on the inner track. North-South trains operated northbound via Wabash Avenue and Lake Street, while southbound they operated via Fifth Avenue (now Wells Street) and Van Buren Street. At the same time, the Northwestern and Chicago & Oak Park lines changed from left- to right-hand running to reduce switching delays at Tower 18. The track configuration at the junction was now considerably more complicated. Met trains simply followed the inner track curve from Lake to Wells. Lake Street trains entering the Loop followed a new track that led them from the eastbound Lake Street track, across the Outer Loop track, and onto the southbound Inner Loop over Wells; they left the Loop from another new track that led them from the inner track over Lake, across the "Outer-Loop-around" and straight southbound Wells track to the westbound Lake Street track. Northbound North-South trains simply took a curve off the outer track, making a right turn to the northbound Northwestern track over Wells; southbound North-South trains simply continued on a straight course over Wells from the Northwestern onto the Outer Loop. There also remained the "Outer-Loop-around" track as mentioned above, now used for South Side trains that terminated in the Loop during off-peak hours.

By the 1920s, Tower 18 was cited as being the busiest railroad junction in the world. A 1927 map issued by the Chicago Rapid Transit Company, citing its "busiest railroad crossing in the world" credentials, said "in the hour of maximum travel 224 trains of 1,244 cars pass through this corner, or 20 cars every minute. The cars passing this crossing in this hour would make a train 10 miles in length." The CRT continued to promote the junction's "world's busiest" status in 1936, when they claimed a train passed through every 15 seconds during the morning rush hour. Extrapolating the traffic levels into a daily measure, they continued, "in a representative day of 24 hours, normal traffic, a total of 2,098 trains, made up of some 6,400 cars, pass this junction. Coupled together in one continuous string, these cars would make a train 59 miles long."2 Tower 18 would be claimed as the busiest railroad junction in the world for some decades after; it is unclear when it lost this claim, or whether this is still the case.

The 1913 configuration of Tower 18 remained for the next 56 years, despite another crosstown route revamp in 1931 and the opening of the State Street Subway in 1943. Only small routing changes occurred. In 1943, Jackson Park-Evanston, Jackson Park-Howard, and Englewood/Normal Park-Ravenswood trains were rerouted into the subway, leaving the Kenwood-Wilson and Wilson-Loop rush hour trains as the only North-South trains running through Tower 18. In 1949, the CTA's North-South service revision brought some of these services back, with all Ravenswood and rush hour Evanston Expresses terminating on the Loop again. In the 1950s, Metropolitan Division trains were slowly siphoned off as well. Logan Square trains were taken off the Inner Loop in 1951 with the opening of the Milwaukee-Dearborn Subway. In 1954, Douglas trains were rerouted via the Lake Street elevated, and thus began following their routing through Tower 18. In 1958, Douglas and Garfield trains were removed from the Loop entirely and placed in a subway as part of the West-Northwest Route. Now only Ravenswood, Evanston Express, and Lake trains remained, the latter of whose routing on the Loop had never changed since 1913. The only additional change of significance took place on September 6, 1961, when the "Outer-Loop-around" track was removed from service.

Up until the 1950s, Wells Street Bridge was controlled from North Water Tower, across the river. North Water Tower was closed on August 10, 1956, with the operating controls for the Wells Street Bridge then transferred to Tower 18. From this point until 1969, there were two interlocking machines and panels in the tower to control the switches at the junction -- both were United Switch & Signal (US&S) Model 14 units -- as well as another panel suspended from the ceiling that controlled the the Wells Street Bridge and Lake Street Bridge.3 One of the two Model 14 EP machines in Tower 18 controlled the junction -- that machine had 11 levers. The other machine had seven levers and controlled two crossovers: one just south of Randolph/Wells, and one just east of the junction on Lake Street at LaSalle. This second machine was used to switch Ravenswood trains to and from the Inner Loop track during off-periods when all trains were routed via the Inner Loop to save the cost of several agents on the Outer Loop. As such, it may have been installed early in the CTA period (this routing was instituted on January 15, 1950).4


Tower 18 Replaced and Relocated

In 1969, the old Tower 18 became a casualty of progress. Its location in the middle of the intersection was ideal for watching over the action of the junction. But it also put it in the path of the new eastbound Lake-Dan Ryan track that was necessary for the new through-route. A new tower was needed clear of the right-of-way and so the old two-story frame structure was phased out of service on September 6, 1969 and dismantled soon thereafter. The next day, the new, modern Tower 18 was placed in service. At the same time, the controls for the Washington/Wells crossover two blocks south were moved from Tower 18 to the temporary Tower 19 (at Washington).

The Changing of the Guard: A two-car Lake "B" train of 2000-series Pullman cars passes the old and new Tower 18 at Lake & Wells in June 1969. The new tower was built to accommodate a reconfiguration of the junction necessitated by the new Dan Ryan Line. By the end of the year, Lake trains would be through-routed to the new Dan Ryan Line. For a larger view, click here. (Photo by Jerry Appleman)

On September 28th, the new Lake-Dan Ryan routing took effect. The Loop's operating plan was significantly altered again. The Loop returned to a bidirectional railroad, but used right-hand operation this time. The track configuration at Tower 18 was again altered for the new routings. Now, the north-south Ravenswood tracks above Wells both continued straight through the junction to become the inner and outer Loop tracks on the Wells leg. Likewise, the east-west Lake Street Line tracks continued straight through the interlocking, becoming the inner and outer Loop tracks over Lake Street; the new Lake-Dan Ryan route used these straight tracks over Lake in both directions. Right-turn curves were provided on all sides, except from SB Wells onto WB Lake, as no trains ran there. (It should be noted, however, that no revenue trains ran from EB Lake to SB Wells, although a curve was provided there. It is only used on rare occasions when Lake trains must be terminated around the Outer Loop.) Additionally, a left-turn curve was provided from SB Wells to EB Lake for Evanston Expresses, which operated clockwise on the Inner Loop. Ravenswood trains were assigned to operate counterclockwise on the Outer Loop; they entered the Loop continuing southbound on the west track from the Ravenswood Line to the outer Loop track over Wells, and left the Loop by turning north from the Outer Loop track over Lake onto the east northbound Ravenswood Line track over Wells. On September 30, a new Loop Shuttle was introduced to help Lake-Dan Ryan passengers access the Wells and Van Buren sides of the Loop. The shuttle operated on a continuous clockwise circuit around the Inner Loop, but was short-lived: the Loop Shuttle service was eliminated in 1977.

The new tower building was a two-story metal L-shaped building. Situated on the northwest corner of the junction, it was suspended off the side of the structure, keeping it clear of any tracks, present or future (it is very unlikely there will ever be a SB Wells-to-WB Lake curve). Like the old tower, access to the second floor control room was via an exterior staircase. Windows on three sides of the building gave a good view of all sides, except the Lake Street Line. Controls were now fully electronic.

A few changes took place at Tower 18 between the 1969 remodeling and the renewal of the junction and Loop signals in the late 2000s. The "Inner-Loop-around" track went out of revenue service in 1977, but remained in place. That routing was returned to service in 1993, when the new Orange Line began terminating clockwise around the Inner Loop.

Over Labor Day 1996, CTA changed out Tower 18's 90-pound rail with 115-pound components as part of an improvement project. Most of the switches were changed from air to electric operation at that time. Also begun was work on a new "Outer-Loop-around" track connecting westbound Lake Street with southbound Wells Street. Although this routing is not used in any current regular operations, it is helpful because it allows Brown Line trains (which operate on the Outer Loop) to be sent back around for additional trips around the Loop should the Wells Street bridge be up for a passing vessel, likewise for northbound Green Line trains and the Lake Street Bridge. Also installed in this project was a new eastbound Lake-to-southbound Wells track, allowing southbound Green Line trains to be routed around the Outer Loop via Wells and Van Buren, if desired. On November 23, 1997, the new interlocking plant was officially placed in service at Tower 18. Upon completion, Tower 18 became a "5/8 grand union" junction.

The CTA continued adding tracks to Tower 18, making the junction more versatile and flexible for Loop operations. In mid-2004, the CTA began installing a northbound Wells-to-westbound Lake Street track. In Summer 2004, new cross-timbers to support the track were installed and in early Fall a new switch was added on Lake Street west of the junction to connect to the new track. The new curved track was installed over the weekend of October 16-17, 2006, requiring much of the Junction 18 interlocking plant to be removed from service. As a result, that weekend the tracks between Tower 18 and Washington/Wells were removed from service and the Brown and Orange lines were through-routed, restricted to 6-car trains, via Lake and Wabash. Although no service made regular use the track at the time of its installation, it allowed Lake Street Green Line trains to be short-turned around the Inner Loop or operate via Wells and Van Buren rather than Lake and Wabash. Eventually, it came to be used for the CTA's 54th Avenue-Loop service, dubbed the Pink Line. Beginning operation on June 25, 2006, the Pink Line is a reroute of Douglas branch service to downtown via Lake Street and the Paulina Connector, terminating around the Inner Loop and turning from north to west at Tower 18 for the return trip back to 54th/Cermak.


Loop Signal Replacement Project and a New Tower

On January 10, 2007, the Chicago Transit Board approved a $48.2 million contract to replace the signal and train control systems along the Loop Elevated tracks. The new train control system replaced a system that was 31 years old and enhanced CTA's ability to operate trains through Tower 12 and Tower 18 junctions. The new systems help to improve the reliability of service by regulating train movement, speed and intervals at those junctions.

The new relay house and equipment facility for Tower 18, including an auxiliary control room, is seen looking north along Wells Street on November 21. 2009. For a larger view, click here. (Photo by Graham Garfield)

Divane Brothers Electric Company was selected following a competitive bid process. Funding for the project came from the Federal Transit Administration (FTA), the Regional Transportation Authority (RTA) and CTA bonds.

Work was expected to begin early in 2007 and be completed in 2009.5 However, problems with the contractor's performance6 7 8 and the broadening of the project scope to include track renewal on the Lake and Wabash sides of the Loop delayed the project, which was not substantially completed until July 2011.9 In addition, the total contract value increased to $67.9 million, with a total project budget of $103.2 million.

The Loop Signal Project included a new bidirectional cab signal system for the Loop Elevated, a new Tower 18 at Lake and Wells, a new interlocking at Jefferson on the Lake branch, a signal facility building for Tower 18 where the old Randolph/Wells station platforms were, and a new Tower 12 relay house, plus new control panels for Tower 12 and Jefferson Crossover. A portion of the bridge control system that operates the Lake and Wells Street bridges was also upgraded.

Junction 18 is seen looking northwest from above on November 21, 2009, as a Cottage Grove-bound Green Line train passes through. It's an average scene at this location except for one thing: there's no Tower 18! The old tower building has been removed in advance of the new one's installation, and the interlocking is being controlled from the auxiliary control room immediately to the south. For a larger view, click here. (Photo by Graham Garfield)

A new platform was constructed in 2008 at the former location of the remnants of the north end of the Randolph/Wells Outer Loop platform, stretching between Lake and Randolph on the west side of the tracks. The new structure was constructed to support a new relay house and ancillary control facility for Tower 18, both for the used during the construction of the new tower and after the new permanent interlocking was in place. The prefabricated buildings -- long, one-story arched-roof metal enclosures -- were lifted into place on January 25, 2009. The new equipment was wired in and brought online over the next 10 months.

Control of the Tower 18 interlocking was switched over from the old tower to the new relay house on November 16, 2009. Over the weekend of November 14-15, while the changeover was taking place, the switches in the interlocking were clamped into one position and trains were rerouted, with Orange and Brown line trains through-routed via the Lake and Wabash legs, while the Green and Pink lines were routed via the Wells and Van Buren sides; Pink Line trains terminated at Roosevelt. The new relay house was built with a temporary tower room and control panel, with monitors to watch the various approaches via cameras mounted on tall poles around the interlocking plant.

After the old tower was removed from service, the 1969-vintage building was demolished within one week. By Monday morning, November 23, a new pre-fabricated tower building had been lifted into place, in the same location in the northwest corner of the interlocking outboard of the tracks that the previous tower had been. During late 2009 and early 2010, work continued on wiring the new Tower 18 into the interlocking and replacing switches and relays at Tower 12.

On Sunday morning, May 16, 2010, the towerman moved from the relay house into the new tower and began to control the interlocking from the new facility while testing of the new tower panel and training of the tower personnel was completed. The new Tower 18 control facility was officially placed in service at 5am, Wednesday, May 19, 2010.

Tower 18's remote control of Jefferson Interlocking, immediately west of Clinton station on the Lake branch of the Green and Pink lines, a 1/2-mile west of Tower 18, was activated on Wednesday afternoon, December 12, 2012. Jefferson Interlocking is commonly used to turn back inbound trains when the Lake Street Bridge is up or during other service disruptions.


Tower 18 Track Renewal and Wells Street Bridge Rehabilitation

On July 15, 2011, the Chicago Transit Board approved a $33.8 million contract to begin work on the second half of the Loop Track Renewal project, which involved the replacement of deteriorated track and rail ties along the Wells and Van Buren elevated tracks. Portions of the Loop Elevated system that underwent renewal work in this next phase of work included the Tower 18 and Tower 12 junctions. The project also included replacement of other rail system components including foot walks, traction power and signal cabling, signal panels, switch machines, and rail lubricators.

Ragnar Benson Construction, LLC was awarded the contract through a competitive bid process. Funding for the Loop Track Renewal project was provided by a state grant through the RTA. Work began in late 2011 and was planned to be completed in late 2012, but the work at Tower 18 and on the Brown Line at Hubbard Curve just north of the Loop was deferred to piggyback on another project.

The Chicago Department of Transportation (CDOT) performed a ear-long reconstruction of the historic Wells Street Bridge in 2012-13, during which the CTA took the opportunity to perform track renewal at Tower 18 and on the Brown Line from the Loop and through Hubbard Curve north of Merchandise Mart station.

The bridge's historic elements, railings, bridge houses and major structural components will be replaced to preserve the 1920s look of the bridge. Crews will replace the trusses and all of the steel framing for the lower level road and upper level railway structures. The mechanical and electrical components will also be replaced. The bridge contractor, Walsh/II in One (JV), began work on November 5, 2012, and was expected to be complete by the end of November 2013. Southbound vehicular and pedestrian traffic on Wells was rerouted, including the CTA buses.

While the roadway was closed for the duration of the project, the construction work was designed to keep CTA rail service interruptions at a minimum. "L" trains continued to use the bridge during the project, except for two nine-day service interruptions in Spring 2013, when the CTA rebuilt the Tower 18 Loop 'L' junction at Lake and Wells streets. That work required two nine-day closures of the Wells bridge to Brown and Purple line trains, one in early March 2013, the other in late April.

The Tower 18 work was originally scheduled to be part of the Loop Track Renewal project, which was undertaken between April and November 2012. But by performing the work while CDOT completes the Wells Street Bridge repairs, CTA reduced the duration of the work by eight days. Additionally, combining the work saved CDOT and CTA $500,000 in construction coordination cost.

During the two nine-day closures, which ran from early morning Saturday through early Monday of the following week, alternative bus and rail service was provided. On weekdays, Brown Line trains alternated between terminating at Merchandise Mart station or continuing into Downtown through the State Street Subway. Bus shuttles were available from the Mart as well as special shuttle service on the Loop Elevated.



A four-car Pink Line train of 2600-series cars passes through the Tower 18 interlocking on its way into the Loop in this view looking west on November 30, 2011. A group of CTA signal maintainers is on the tracks next to the train. The interlocking tower was relatively new, brought into service only about a year and a half before. For a larger view, click here. (Photo by Graham Garfield)

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The original turn of the century-vintage Tower 18 has survived into a new era, as it watches over a demonstration run of the modern PCC 6000-series cars on August 16, 1950. Although the rear car bears a Logan Square route sign, it is actually turning north from the Outer Loop onto the Ravenswood Line as a Lake Street train of wooden cars leaves the junction heading west to Forest Park. The 6000s wear a paint scheme variation that were only used for a short time on the first four cars, 6001-6004. (Photo from the Krambles-Peterson Archive)

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Two Lake-Dan Ryan trains -- both 2-car trains of 2000-series cars in the Bicentennial paint scheme -- pass each other at the post-1969 Tower 18 during the midday service lull. The near train is a "B" train heading into the Loop on its way to 95th Street; the far train is on its way back to Oak Park and Harlem Terminal. (Photo from the Chicago Transit Authority Collection)

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A view of Tower 18, looking south in the early 1980s. A four-car Evanston Express train, led by the two 1-50s and trailed by a 6000-series pair, is about the enter the junction as it pulls away from the Randolph/Wells station in the upper right corner. Although the Randolph station would remain open for another decade, the north end is already being used for storage and to house equipment sheds. (Photo from the Chicago Transit Authority Collection)

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Bicentennial unit 1776 -- the Ben Franklin -- passes through Tower 18 on August 1, 1975 on its way to Harlem Terminal on the Lake-Dan Ryan. Meanwhile, a 2-car PCC train, probably a Ravenswood, waits on Wells for the Lake-Dan Ryan to clear the interlocking. (Photo from the Chicago Transit Authority Collection)

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The More Things Change, The More They Stay the Same: The tower, routings, and track configuration have changed in the two decades since the photo above but the equipment is the same, as three two-car Bicentennial 6000-series trains pass through Tower 18 simultaneously on August 1, 1975 in the only way to do so: cars 6033-6034 "Thomas McKean" (left) head straight through on the Ravenswood All-Stop run into Randolph/Wells (visible in the lower left corner); cars 6031-6032 "John Parker" (front right) turn east on the Inner Loop on the Loop Shuttle; and cars 6017-6018 "Haym Salomon" (back right) turn north onto the Ravenswood on their way to Kimball after completing a circuit on the Loop. (Photo from the Chicago Transit Authority Collection)

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After completing its circuit around the Loop and passing through Tower 18, a two-car train of 4000-series Plushie cars heads westbound on a Lake Street "A" run toward Harlem in April 1964. Note that Tower 18 is in the middle of the junction and the track on the right -- the eastbound Lake Street track, dead ends after the switch to the Outer Loop. Five years later, this track would be extended through to allow through-service over Lake Street onto the Inner Loop for Lake-Dan Ryan service. (Photo by Jerry Appleman)

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Looking east out of the old Tower 18 towards the Clark & Lake station in the 1960s. (Photo by Peter Christy)

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Looking south out of the old Tower 18 towards the Randolph & Wells station in the 1960s. (Photo by Peter Christy)

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Looking west out of the old Tower 18 out the Lake Street Line in the 1960s. The trestle bridge over the Chicago & North Western can be seen in the distance. (Photo by Peter Christy)

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An interior view of the old Tower 18 in the 1960s, showing the interlocking controls, desks, and other facility accouterments. The control panel suspended from the ceiling on the right controlled the Lake and Wells bridges. (Photo by Peter Christy)

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A low-lit view inside Tower 18, looking north out a set of windows towards the Chicago River as a train of North Shore Line Silverliners pass on their way north to Milwaukee or Mundelein. (Photo by Peter Christy)

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Looking west out the Lake Street Line from Tower 18 as the setting sun creates a beautiful golden sunset. (Photo by Peter Christy)

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This view looks out the front door window late one rainy night in 1962. You can see a Ravenswood ready to depart the Clark & Lake station. The towerman, before taking this photo, has already set the "inner-to-outer Loop" crossovers and dropped the signal for him. From the back of the targets, we see blue and white lenses, rather than red and green aspects. Notice that both targets are showing red-over-green (or blue-over-white, from this side). The Loop was considered the "Main", or normal, routing. So if a train was being routed off the Loop, the switches were aligned to "Reverse" routing, and the signals (aka "targets") showed a red-over-green aspect. The target positioned closer to the tower is for the Lake Street Line. Technically, it should probably be set for red-over-red, but the towermen at the time usually didn't do that if they knew a Lake train was following the Ravenswood, and was due off the Loop before the next Ravenswood was due on. (Photo by and information from Peter Christy)

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This view looking north from inside Tower 18 not only shows an inbound North Shore Line train, its reflection framed in the open window, but one can also see an inbound Lake Street train, just crossing the bridge, reflected in the "side-view" mirror. The strategically placed "side-view" mirror allowed towermen to see what was going on behind them to the west while looking north, and while looking east a "rearview" mirror mounted on the wall, just to the right of the door, allowed then to see what was going on behind to the west. Typically, they didn't spend much time looking south, since those trains were going away from them. But, with just a little head movement to look from east to north (and being able to see south at the same time), they could keep track of the speeds and positions of the traffic entering the Loop, and time their moves to facilitate the flow. (Photo by and information from Peter Christy)

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This 1962 view is similar to another shot above, showing an outbound North Shore Line Silverliner. The towermen at Tower 18 would only need to worry about the North Shore Line's trains for less than a year before the interurban ceased operations. (Photo by Peter Christy)

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Looking to the south through the bay-window from the seat behind the console in 1962, several details are visible besides the Randolph & Wells station in the background. The "Inner Loop around" curve is still in place at this point and you can see the pneumatic switch cylinder at trackside just to the left of the points. The two nearby targets (you can see the light shining through their blue lenses) are "backup" signals. These were only used to direct trains back against the normal flow of traffic when some unusual circumstance required it. On the west (right) side of the Randolph & Wells station platform, you can see a light inside the bay window of the station house that intrudes onto the platform. This was the Randolph & Wells Supervisor's Office. It was pretty easy to see when the Supervisor was in because he'd be silhouetted right in the center of the window. Further down the line, between the tracks, you can see the green aspect glow of a signal. This was the target for the Lake Street trains, protecting the Outer-to-Inner Ravenswood crossover. (Photo by and information from Peter Christy)

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This 1962 view of Tower 18's interlocking machine shows the interlocking levers (Red = Signal, Red-Yellow = Signal & Trip, Black = Switch) used for the "outlying" switches (e.g. the outer-to-inner, and inner-to-outer Loop switches to route Ravenswood trains during non-rush hour). (Photo by and information from Peter Christy)

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This view from 1962 shows the Union Switch & Signal Company machine used to "give power" to the two City of Chicago bridge tenders. The CTA didn't want to allow the City employees to have full control of the bridges over the Chicago River used for CTA traffic. If one of the bridge tenders saw that he was going to have to raise his bridge, he'd ring up Tower 18 (using a hand crank telephone) to advise the towerman, who'd go through a sequence that would set signals to red, raise the track trips, set the switches to route into bumping blocks, and finally close circuits that feed power into the massive steel bars that hold the two sides of the bridge locked together, while also closing circuits that feed power to the Bridge Tender's controls. Then, and only then, was the city bridge Tender able to operate his controls to lift the bridge. The box on the Interlocking console, next to the telephone, was the "squawk-box." By flipping the appropriate switch. the towermen were in instant contact with the Supervisor's Office at Randolph & Wells or Clark & Lake, or with the Power Supervisor at the Merchandise Mart. The microphone sat on the console to the right of the telephone. The loud speaker was mounted overhead. This arrangement could be a little unnerving when one would suddenly hear a booming "voice from above" when one of these gentlemen wanted to contact you. (Photo by and information from Peter Christy)

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Looking west at Tower 18 from the Clark/Lake outer platform in March 2002 as an East 63rd branch Green Line train passes through the interlocking into the Loop. (Photo by Robert Mencher)

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This view shows how Tower 18 looks contemporarily looking east from the Lake Street approach to the Loop. Barely visible on the right is the Lake-to-Outer Loop curve, which is not used in regular operations, but is brought into service when Lake trains need to be short-turned on the Loop and during certain other unusual moves. The external stairway from track-level to the second floor of the tower, where the interlocking panel and other control equipment is located, is evident. Clark/Lake station is visible in the background. (Photo by Graham Garfield)

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Until the Lake Line was through-routed with the Dan Ryan Line in 1969, it terminated around the Loop. Starting in 1913, it operated counterclockwise on the Inner Loop. Here, car 4407 leads a Lake "B" train through the Tower 18 interlocking, across the Outer Loop track (by this point used primarily by Ravenswood trains) toward Randolph/Wells in January 1964. (Collection of Joe Testagrose)

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After completing a circuit around the Inner Loop, an Evanston Express train led by car 4446 heads north through Tower 18 at Lake & Wells after stopping at Randolph/Wells (seen in the background) on October 3, 1972. (Photo by Steve Zabel, Collection of Joe Testagrose)

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This April 4, 2002 view shows Tower 18 as seen from the Wells Street approach to the Loop, looking south. (Photo by Graham Garfield)

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A Brown Line train trailed by 3200-series car 3208 leaves the Loop to head north toward Kimball, crossing through Tower 18, on May 8, 2002. (Photo by Ernie Baudler)

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Two Purple Line trains -- the one on the right heading northbound to Evanston, the one on the left southbound into the Loop -- pass each other just north of Tower 18 at Lake and Wells on May 8, 2002. (Photo by Ernie Baudler)

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An eastbound Green Line train of 2400-series cars waits for a northbound Purple Line express train bound for Evanston to cross the junction of Tower 18 on May 8, 2002. (Photo by Ernie Baudler)

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An eastbound Green Line train bound for the East 63rd branch approaches the "tic-tac-toe" crosshatch of tracks that makes up one the busiest railroad intersections in the country, Tower 18, on May 8, 2002. (Photo by Ernie Baudler)

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Tower 18 and the junction it controls is seen looking west on Lake Street on June 19, 2006. The X10 home signal governing the westbound track and the position of the switchpoints the signal governs show that the the tour has a route in for the Brown Line, turning from west on Lake to north on Wells. (Photo by William Davidson)

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Car 2208 leads a 4-car rush hour Pink Line train, making the turn at Tower 18 from the Inner Loop onto the Lake branch for the trip back to 54/Cermak on June 30, 2006, five days after the route began service. The last four cars -- 3007-08 -- are wrapped in pink and were one of three 2-car units used for the ceremonial inaugural train for the Pink Line on June 24, 2006. The 2200s' use on the Pink Line marks the cars' first regular use in scheduled service on the Loop since the cars were reassigned off the West-South Route in 1983. (Photo by Graham Garfield)

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A crane has finished lifting and lowering the new prefabricated relay house and auxiliary equipment facility for Tower 18 into place on its platform south of the junction, seen looking north from Washington/Wells on the evening of January 25, 2009. Train traffic between Washington/Wells and Tower 18 was suspended for the day to allow the work to take place. (Photo by Graham Garfield)
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A Brown Line train is rounding the curve at Tower 18 on its way back north to Kimball in this scene looking northwest on January 26, 2010. The new tower's structure is in place, but the building is still being built out, as evidenced by the sections of exterior panelling yet to be installed and the lack of windows at the control room level. (Photo by Graham Garfield)
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The new Tower 18 is nearly ready for use as a Brown Line train approaches on its way into the Loop, looking northwest on May 1, 2010. The building is so new, the manufacturer's decals are still on the window glass. Although some work was still yet to be done, the new tower would be controlling the interlocking again about two weeks later. (Photo by Graham Garfield)
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All four Cubs World Series cars -- in order from the front (left), 5695-5996-5304-5303 -- wrap around the Inner Loop-to-westbound Lake Street curve normally used by Pink Line trains at Tower 18 on April 23, 2017, while running on a private charter. (Photo by David Harrison)



  1. Moffat, Bruce, The "L": The Development of Chicago's Rapid Transit System, 1888-1932 (Bulletin 131). Chicago: Central Electric Railfans' Association, 1995, 177.
  2. "'L' Loop Crossing Is World's Busiest", Go on the "L" newsletter, Vol. 1 No. 1, February 15, 1936, pg. 2
  3. Correspondence with Kendrick Bisset, former CTA Director, Power and Way Engineering, 2011 April 29-30.
  4. Ibid, 2012 January 29-February 5.
  5. "Construction Project Briefing." Report to the Chicago Transit Board. 2011 July 15, pg. 7.
  6. "Problems in Loop could further delay CTA project." Chicago Tribune. 2008 September 11.
  7. "Loop L signal work delayed." Chicago Sun-Times. 2008 September 11.
  8. "CTA work may be delayed by year." WLS-TV Chicago online. 2008 September 11.
  9. "Construction Project Briefing." Ibid.