St. Joseph Swing Bridge

This massive bridge crosses the Missouri River at St. Joseph, Missouri. It carries a Union Pacific spur across the river, and is used quite sparingly.
The main span of the bridge is a swing span, which features two leafs of Subdivided Warren Through Truss, each containing 6 panels and riveted connections. These spans are joined together over a pivot point; set onto a round concrete pier.
On the west side, the bridge is approached by three Pennsylvania Through Truss spans; with pinned connections. The two closest to the river are 298 feet in length, while the western span is 295 feet in length. All three of these spans feature 12 panels.
The substructures for these spans are built of concrete. In addition, the east side contains a pair of deck girder spans; one at 60 feet and one at 80 feet.

Blueprints of the bridge, from Railroad Gazette: Volume 48 Issue 2

The bridge appears to have been built by American Bridge Company; as a missing plaque on the west approach indicates. However, it is possible that this bridge also had one or more other contractors to help with the various stages of construction.
While the bridge was originally built 1904 using older stone piers, the bridge was extensively upgraded by early 1919. These upgrades included the replacements of the stone piers, the replacement of the swing span with a larger structure, and the shifting of all approaches towards the shores to accommodate the larger swing span.
Due to the limited use, this bridge sees an uncertain future. Crossing a navigable waterway makes for a tough situation; and if Union Pacific ever decided to stop using the structure, the Army Corps of Engineers would likely require the historic structure to be removed.
Despite this, there are limited examples of rail-trail projects reusing former movable bridges. One of such examples is a planned project in Boonville, Missouri. It is hoped that when abandoned, this bridge can be kept in use as a pedestrian trail should UP ever discontinue the line.

The author has ranked this bridge as being regionally significant; due to the limited number of remaining crossings of the Missouri River which are historic in nature. The upstream crossing at Rulo was replaced in the 1970s, while the bridges at Leavenworth were removed as well.
Fortunately, this bridge appears to be in sound condition; namely with the trusses demonstrating a high level of integrity.
The photo above is an overview from the Missouri side of the river. The photo below is a detail of the main swing span. These photos were taken in September 2016, on a cloudy morning. The author hopes to return for better photos soon.