Blair Railroad Bridge

View an article describing the construction of this bridge

Located along US Highway 30 in Blair, this large through truss bridge carries the Union Pacific mainline across the Missouri River. A bridge connecting the existing railroad line at Missouri Valley, Iowa to the Union Pacific Railroad at Fremont had been planned since November 1881. At this time, officials of the Sioux City and Pacific met with George S. Morison at the site of the existing ferry at Blair, Nebraska. Morison was a renowned bridge engineer, who had just completed a crossing at Plattsmouth, Nebraska and was currently working on another structure at Bismarck, North Dakota. The Missouri River at this location is not bounded by bluffs on either side, leading to an often shifting course. To construct a permanent bridge at this location, alterations would be required to prevent the river from changing course. Morison evaluated the site: "While control of the river might be unusually difficult, the construction and maintenance of the bridge itself would be a comparatively simple thing". Morison developed a proposal to construct a Whipple through truss bridge, similar to the Plattsmouth and Bismarck bridges.

In June 1882, the plan was approved by the Secretary of War. Morison contracted with Saulpaugh & Company to construct the stone piers for the bridge, and Keystone Bridge Company was selected to fabricate the superstructure. During the summer of 1882, a dike was constructed on the east end of the bridge, and other improvements related to channel control were constructed. Both banks would use stone rip-rap, placed into wire baskets to stabilize the banks of the river. Work on the stone piers began in October 1882, and was completed in May 1883. The piers were constructed using limestone quarried at Mankato, Minnesota; and the cutwaters on the center two piers were constructed using granite quarried at St. Cloud, Minnesota. Work quickly began on erecting the superstructure, with the bridge officially completed on October 22nd, 1883. The main spans of the bridge utilized three 330-foot pin connected 15-panel Whipple through truss spans, similar to other Morison spans across the Missouri River. The east approach was constructed of a 110-foot pin-connected Pratt deck truss, and a 22-foot deck plate girder, set onto a steel caisson pier and stone abutment. The west approach was initially constructed of a 110-foot deck truss of similar design to the east approach. Both ends initially utilized timber trestles until the embankments could be stabilized. Typical of other bridges designed by Morison, the bridge utilized a varying steel content. Steel had not yet become the primary metal of bridge construction, and was still being tested. The first Missouri River bridge designed by Morison at Plattsmouth utilized approximately 58% steel content in the main truss span. Approximately 37% of the Whipple trusses on this bridge would be fabricated from steel.

The west approach trestle was filled during the construction of the bridge. The west embankment settled significantly between 1883 and 1885, leading to the replacement of the west truss with a 176-foot span of similar design. The east trestle could not be filled until cut material from the Nebraska side of the bridge could be brought across. The trestle was finally filled in 1885. Issues with the east approach initially arose during the 1890s, when shifting of the caisson pier on the east approach was noticed. Repeated attempts were made to correct the issue, and a large amount of stone from the abutments of a replaced bridge near Missouri Valley was installed near the caisson pier.

By the early 1920s, the bridge had become too light for the heavy loads required by railroads. Plans were made to replace the bridge, and in 1923, a contract was awarded to American Bridge Company to fabricate a new steel bridge that utilized the existing stone piers. The main spans of the bridge would be 330-foot riveted 10-panel Parker through trusses, utilizing heavily constructed members. The east approach would be reconstructed with a 111-foot deck plate girder, and a 22-foot deck plate girder. New concrete would be added to the east abutment, and the steel caisson piers reused. The west approach would be replaced with a pair of 89-foot deck plate girder spans, and a 22-foot deck girder span. These spans would be set onto a steel bent and concrete substructures. Work on the bridge was completed in January 1924. Work was completed with minimal interruption to railroad traffic. The old spans were found to be in good condition, and the 330-foot spans would be reused. One of the three spans was immediately assigned to be reused at Bridge #S-1480 across the Wind River near Riverton, Wyoming. As of 2024, this span is in use as a trail. The remaining two spans would be shortened to 242-feet and installed at Bridge #S-1493, also across the Wind River at Riverton. The old deck trusses were scrapped, with the stringers being reused for falsework.

The east approach was a continuous problem for the railroad. Due to the shifting westwards of the slope, the cylinder pier was continuously shifting. In approximately 1960, the 22-foot span would be replaced by a 30-foot span, and a new concrete abutment constructed. Additional rehabilitation work has been completed on the stone piers, with concrete caps added in approximately 1990. Union Pacific has made significant upgrades to this route, as it provides a direct connection between the mainline at Fremont and the mainline to Chicago. There is speculation that this bridge may be replaced, or that a twin span may be constructed alongside it. Currently, there are no known plans for replacement or an additional bridge. Overall, the bridge appears to be in fair to good condition, with no significant deterioration noted. The author has ranked this bridge as being highly significant, due to the large size of the trusses.