CDOT's Movable Bridges on the Calumet River
There are 5 movable bridges operated by CDOT on the Calumet River. Unlike the Chicago River bridges which, for the most part, are operated on a fixed schedule, these are operated on demand. And boy, are they operated - a total of 22,860 lifts in 2015.
For comparison, consider the regularly operated CDOT bridges on the Main Stem and the South Branch of the Chicago River. The annual number of lifts for these 27 bridges is roughly 1,100. CDOT's 5 Calumet River bridges are operated about 21,000 times more (or by a factor of 20) each year than the 27 movable Chicago river bridges.