MIDWEST INTERLOCKING TOWERS
EARLY INTERLOCKING TOWERS
Early interlockings in Illinois and each neighboring state, according to annual reports from the various states' railroad commissions.
Early Illinois Interlocking Towers (1800's)
Early Illinois Interlocking Towers (1900's)
Early Indiana Interlocking Towers
Early Michigan Interlocking Towers
Early Wisconsin Interlocking Towers
Zoomable Google Maps for the Chicago area marked with present and past railroad junctions, crossings, and towers.
The number of active interlocking towers is dwindling, as more control is transferred to CTC installations. But Chicago still has one of the highest concentrations of active towers.
Chicago's Interlockings (Background)