This bridge was originally built by the Peoria, Decatur and Evansville Railroad, later taken over by the Illinois Central.
As you can see the right side pylon is round and was designed to swing the span open for steamer traffic.
From my research, it hasn't been opened since it was tested when built in 1888. The Wabash River used to be navigable and many of the original spans swung open, were suspended or have high clearance to allow passage as far north as Terre Haute. As I have read, the bridge tender would walk out and unlock the span and a mule would pull the span open for passing ships.
The left side collapsed in 2000 during a flood when the Wabash channel shifted west.

This is why the abandoned New Harmony Bridge (a few miles north) span has such a high clearance.

The Big Four (CCC& StL Railroad) Evansville Secondary bridge at Mt Carmel has a swing span in the middle. It is still in use for backing coal trains into the Duke Energy plant nearby, but there is no record of this span ever opening. (Sorry, photo is fuzzy). It is now owned by Norfolk Southern.

Next is a bridge in downtown Mt Carmel. Built by the Southern Railroad, the swing span is way over on the left bank. It is almost blocked by trees. Norfolk Southern owns this bridge as well.

This bridge was the Big Four (CCC& StL) Vincennes Secondary and the swing span was in the middle section. It is now owned by a local farmer who operates it as a private toll bridge called "The Wabash Cannonball Bridge". You can drive it yourself. Make sure no one is coming when you start or you will have to backup.

The B&O Southwestern built a swing span at Vincennes in the 1880's, but the Wabash flood in 2000 caused the swing section on the Indiana side to loosen and caused alignment trouble. The current owner is CSX and they had the swing span removed in 2002 and replaced it with a girder plate span.

The bridge at Riverton, Indiana has a center swing span that has not opened. Originally built by the Illinois Central in the 1890's to replace a narrow gauge to Indianapolis, it is now operated by the Indiana Railroad. The span is locked in place as the IR has put welded rail in and there are no breaks for the span to move.

This bridge was originally built by the Peoria & Eastern in the 1890's and has been modified by the current owner CSX. The lift span was centrally located at one time, but CSX replaced it and placed a girder plate in its place.

Since the Wabash River was not considered reliably navigable north of Terre Haute, the waterway access requirement ended there. This waterway requirement remained on the books until after World War 2, whereas it was turned over to the Tennessee Valley Authority. The TVA evaluated it and it was considered not viable for power or water commerce and after removing the dam at Grand Rapids north of Mt Carmel, the water route was formally decommissioned.
The result of this requirement is a bevy of swing and lift spans that never (or rarely) opened. No one can find a record of a steamer coming up the Wabash river after 1900, 10-15 years after most of these bridges were built.
Makes you wonder how many bridge tenders the railroads hired to open and close them, just to have no one come through.