This tower controlled the south end of Union Station, used mainly by the Pennsylvania, Alton, and Burlington railroads. Another tower controlled the north end, used by the Milwaukee Road.

For many years, I commuted via the Burlington (CB&Q, Chicago, Burlington and Quincy; later Burlington Northern).

I believe we're looking at an early "centralized traffic control" module, and the net effect of it was to increase the allowable number of trains on a given track by about 50%, according to Kip Farrington's "Railroads at War". Given that Chicago is a choke point for railroad traffic to this day, this was an incredibly big deal for getting war supplies to the front.

Today there might be an app for that!

This interlocking tower overlooks a portion of the trackage that had encountered a bit of a mishap on March 10, 1954 when the Burlington Zephyr failed to stop at a red signal and collided with the departing Pennsylvania Railroad's Liberty Limited. This would have occurred at the area of trackage shown on the 'model board' or track diagram directly above the clock in the Delano photo. Twelve passengers on the Liberty Limited were treated for minor injuries.

A brakeman should have been stationed at the rear of the Zephyr's observation car where there is a brake valve provided to stop the backing train if needed and it certainly looks like it was needed in this situation. The interlocking tower would be located directly above the photographer in the attached photo.

Looks like the same interlocking machine controller used at the Harris Switch Tower in PA:

These men must have known deep down that if what they were doing depended only on watching the lights on the board, soon enough the men wouldn't be needed.

In the foreground we have Martin Balsam. In the back, we have James Millhollin.