I think there is picture of the bridge (circa 1900) on the Mississippi River and Bonnterre Railroad wiki website. As for the riveted connections I'm sure the bridge has been upgraded to handle modern traffic.
I would estimate this to be an early 1900s bridge. It is a lighter structure than later riveted trusses, but it still shows features of the 20th century. It is possible it was set onto older stone substructures, which could have been built in 1891.
I see riveted connections, which means it's probably later than 1891.
A 1904 USGS map shows this bridge was on the Mississippi River and Bonnterre Railroad line. The bridge was built in 1891.
We used to walk out to the center pillar along the bottom.
The style of postcard is mid 1900s, and already shows riveted connections vs the pinned connections prominent in 1890s bridge construction.
So this isn't an 1891 bridge, but it likely replaced one, so I'll make up an entry for it.