The Split Rock is an interesting area of the I and M Canal in LaSalle County.   During  the construction process at this site, the canal workers blasted a passage through a ridge of limestone.  The  interurban electric line the Chicago, Ottawa, and Peoria constructed a bridge across this passage.

The bridge was a lost Pratt through truss bridge.  It is no longer present.  The photos above are obtained from the internet.

On one side of the passage, the Chicago, and Rock Island constructed a  tunnel through  the rock ridge.