La Crescent Swing Bridge

Located entirely in Minnesota, this bridge is the westernmost span of four bridges crossing the Mississippi River between La Crosse and La Crescent.
The first bridge was built here in 1876, and consisted of a swing span, approached by several stationary trusses. This bridge was connected by trestle to the other three bridges, although the trestle was gradually replaced by earthen fill.

Previous span, showing two spans reused at Eau Claire. From The Railway Age, Volume 34

By 1900, it was required to build a new span at this location. As a result, work began in 1901 to replace all four bridges on this crossing.
This bridge would be rebuilt with a new 360-foot pin connected Through Truss swing span, a 250-foot 9-panel pin connected Parker Through Truss and two 160-foot 6-panel Pratt Through Truss spans. In addition, a 40-foot deck girder was used on the east approach and a 75-foot deck girder on the west approach. The bridge reused some stone substructures, but new concrete abutments were also built.

Constructing the swing span, from The Railway Age, Volume 34

Because of the incredible amount of steel required for this bridge, three contractors were involved with building the four bridges. This bridge and the truss span at French Slough were built entirely by Phoenix Bridge Company, while American Bridge Company and McClintic-Marshall Construction Company built the other structures.
Unfortunately, the truss spans of the East Channel Bridge, French Slough Bridge and the swing span on the Black River Bridge were replaced between 1998 and 2004.
Ranked as one of the most struck bridges on the Mississippi River, this bridge is in an immediate danger of replacement. Barges commonly hit this structure, and the Coast Guard desires to replace the structure with a modern span. Several options have been proposed, including adding a lift span in place of two fixed spans. However with a price tag of over $70 million, the bridge project has not been funded.
Overall, the bridge remains in fair condition, and is showing signs of aging. The west approach appears to have been replaced at some point, although there is no clear evidence of when this may have happened.

Blueprints of the four bridges, from The Railway Age, Volume 34

The author has ranked this bridge as being regionally significant, due to the large scale design.
The photo above is an overview from the west bank.