Between 1871 and 1914, railroads in Illinois were regulated by the Railroad and Warehouse Commission of Illinois. That agency was then succeeded by the Illinois Public Utility Commission. And in 1921 was succeeded by the Illinois Commerce Commission, which continues to regulate electric and gas and telephone utilities.

When it was the Railroad and Warehouse Commission of Illinois, interlocking towers were assigned numbers, in the order in which they were registered with the Commission. This was similar to a numbering system adopted by the Railroad Commission of Texas, for that state. Except in Texas, the towers were actually officially known by the numbers. One of the more famous towers in Texas was "Tower 55", located near downtown Fort Worth.

In these lists, towers are grouped by year registered, and are listed in numerical order. The year registered is not necessarily the year constructed. Also identified are the railroads and the lines involved, which are explained through a separate link below.

Illinois Towers 1889-1899
Illinois Towers 1900-1913

Railroads And Lines

Some interlockings were later eliminated through grade separations.