Snake River Bridge (Idaho Falls, Idaho)

On December 10, 1864 a franchise was granted to Edward M. Morgan, James M. (Matt) Taylor, and William F. Bartlett to operate a ferry one and one-half miles below Cedar Island and build a bridge over Snake River at Black Canyon. Mr. Taylor selected the bridge site and in 1864-65 erected an 83 foot wooden span with solid rock anchorage on both sides. It was a modified queens truss type. The first bridge to cross Snake River was located 1320 feet south of this spot. A replica of the bridge tops this monument.
—Bonneville County, Idaho

And here's the monument with the bridge replica atop it:  

Submitted by @danbrekke