Chicago Transport Authority

by John Hinson

Wilson Avenue tower
Photograph 10/6/58, by Dr. J W F Scrimgeour

Wilson Avenue was the only mechanically-operated tower to survive into later years on what became the Chicago Transit Authority elevated system. At around 1910, the entire system was controlled by over a dozen mechanical towers, but a programme of replacement by US&S electro-pneumatic interlockings commenced around 1913 - see Tower 12 for an example. Wilson Avenue somehow survived these renewals.

This tower controlled crossings and sidings on the quadruple track section between Armitage Avenue and Howard Street.

The tracks are electrified on the third-rail system, and are shared with the Chicago, North Shore & Milwaukee railroad. One of that company's trains is visible on the left of the picture.

The points in the foreground have the switches locked by detector bars - at least one set of these remained at Wilson Avenue through to the closure of the tower and were believed to be the last such in the USA.

Others at Wilson Avenue and elsewhere, were converted to be locked by track circuits. The railroads were required by the Interstate Commerce Commission (now Federal Railway Administration) to remove detector bars by October 1st 1955 , but interestingly the CTA was not governed by the ICC, so the bars survived.

The miniature semaphore signals in front of the tower are not shunting signals - these are running signals of a type adopted on the elevated system for all moves. The small size was convenient to use owing to limited clearances, and short stopping distances meant that a long-distance view was not essential.

Interior of Wilson Avenue tower
Photograph 10/6/58, by Dr. J W F Scrimgeour

This view taken inside Wilson Avenue tower shows the National mechanical lever frame, or rather, interlocking plant, which dated from the opening of the box in 1900. At a later date, this was replaced by a Westinghouse "A" pattern frame.

Wilson Avenue tower closed in the mid-1990s.

Additional notes by Kendrick Bisset

About the photographs

Comments about this article should be addressed to John Hinson