Right here stands Clark Junction Tower a silent yet vital orchestrator of Chicago’s “L” train system. Established on May 18 1907 Clark Junction was built to connect the Ravenswood branch to the North Side Main Line. This junction sits near School Street and Wilton Avenue. It is southwest of Clark and Roscoe.
Clark Junction joins the two-track Ravenswood branch. It meets the four-track North Side Main Line. The inside tracks are express. The outer tracks are local. The branch’s southbound track merges into the southbound local track. The northbound track diverges from the northbound express track.
Originally the first Clark Tower stood at the junction’s north end. It was between the main line and branch tracks. A local station existed at Clark Street just south of Roscoe. The tower was placed at the south end of the southbound station platform. From there workers could oversee the junction. They also watched the approach tracks in all directions.
The original tower was two stories. It had a wedge shape and a hipped roof. It was practical. Decorative window frames sills and belt course moldings added some style. Inside space was tight. Windows gave maximum visibility. A small iron potbelly stove heated the tower. Workers used a hand-operated lever system to control switches and signals. The interior was a dizzying array of levers. A vigilant towerman had to precisely align these switches.
In the mid-1970s the CTA modernized Clark Junction. Semaphore signals gave way to multi-aspect colored light signals. A new spacious interlocking tower was built. This new tower was east of the main line tracks. It rose five stories. The control room was cantilevered over the tracks. Access came from street-level and track-level. The top floor tower room had large picture windows on three sides. This gave the towerman more room and better visibility.
An electric entrance-exit tower panel controlled the new interlocking. Instead of huge mechanical levers workers pressed a few buttons to set routes. The tower cost 249000 dollars. State and federal governments funded the CTA signaling program. The new interlocking plant went into service August 22 1976. The new tower finished a few months later. At that time over 950 trains carrying 130000 people passed through Clark Junction each weekday.
Even with improvements Clark Junction remained busy. Its flat junction layout caused conflicting moves. Northbound Ravenswood now Brown Line trains use the outer local track. To reach the Ravenswood branch they must cross the northbound inner express track. North-South now Red Line trains use that track. Ravenswood trains then take a diverging route. They cross the southbound inner track. Southbound North-South trains use this track. Inbound Evanston Purple Line Express trains also use it during rush hour. This means north- and southbound North-South trains and southbound Evanston Express trains must wait. They wait for the Ravenswood train to cross the at-grade junction. This can take time during rush hour.
In the early 2000s a short section of northbound track at Clark Junction saw up to 40 trains per hour. That is 20 northbound Brown Line trains and 20 northbound Red Line trains. In 2002 Clark Junction served 876 trains each weekday. It was the CTA’s busiest rail crossing on a 24-hour basis.
As part of the Brown Line Capacity Expansion Project the signal system was upgraded. On October 14 2004 the Chicago Transit Board approved a 45.5 million dollar construction contract. New signal equipment was installed along the tracks. Clark Tower was rehabilitated.
During 2005 and 2006 single-track and reroute operations were required. Contractors installed new crossovers. They laid signal and communication lines. The new Lakewood-Seminary Interlocking came on-line March 29 2006.
In April 2006 a new relay house was installed north of the tower. While the tower was being renovated control of Clark Junction moved to a local panel in the relay house. Control was slowly cut over during the summer of 2006. For about a month control was split between the tower and the relay house. Two towermen were needed to establish train routes. Close coordination was essential.
Renovation included a new larger tower panel. This panel allows remote control of all interlocked crossovers from Addison and Lakewood to Armitage. Work at Clark Junction finished in late 2006. In November 2006 control of Clark Junction returned to the newly rehabilitated Clark Tower.
In 2018 the CTA began demolition for the Red-Purple Bypass Project. The total project cost is pegged at 570 million dollars. The bypass will allow more trains to run on the Red Line. It will reduce overcrowding.
Clark Junction Tower stands as a testament to Chicago’s ever-evolving public transportation. Its history reflects the city’s commitment to moving people efficiently.