Northern Pacific Railway Bridge #9

Located between the 10th Avenue Bridge and the Washington Avenue Bridge, this unique deck truss bridge carries a pedestrian trail across the Mississippi River. The first bridge #9 featured a pair of 245-foot 8-panel pin connected Pratt deck trusses, approached by a deck plate girder viaduct of alternating 60-foot spans and 30-foot tower spans. The tower spans were reinforced with kingpost trusses, and the bridge bridge constructed of wrought iron. When constructed, the 30-foot truss panels were believed to have been longer than any previously constructed in the United States.

As railroad traffic increased and the University of Minnesota grew, a grade separation solution needed to maintain safe railroad operations. An order to depress the tracks through the area was issued in 1909, but the issue was not taken up by City Engineer Frederick William Cappelen until 1918. An agreement to relocate the tracks and construct a new bridge was reached in 1922. The new bridge would reuse the two trusses from the previous bridge. The old bridge was removed, and the trusses strengthened by Minneapolis Steel & Machinery Company. American Bridge Company fabricated third truss lines to add load capacity to the trusses, as well as five deck plate girder approach spans. Construction on the new bridge began in May 1922, and would be completed by December 1924. Frankman Brothers Construction Company constructed the substructures and erected the bridge.

When completed, the new double track bridge featured, from south to north, three 90-foot deck plate girder spans, the two deck truss spans, and an 85-foot and 80-foot deck plate girder span. The truss spans reused the stringers, floorbeams and trusses from the original 1885 bridge, and the pinholes were rebored during the strengthening. A riveted truss line was added to the middle of the 1885 trusses, which greatly increased the strength of the spans. The entire bridge was set onto concrete substructures, and an eight-degree curve was constructed in the south end of the bridge.

Reusing spans was not an uncommon practice for railroads. Often, old spans which did not have sufficient capacity for mainline use could be reused on branch lines. However, this bridge is an oddity, as the old bridge was reused in the successor. The remaining girder spans from the 1885 bridge were reused at various locations throughout Montana, where many still exist.

Overall, the bridge is in fair condition. Work has been ongoing since 2014 to stabilize the substructures, including repairing the existing concrete. The author is glad that the City of Minneapolis has chosen to rehabilitate this bridge and preserve it for years to come. The author has ranked this bridge as being highly significant, due to the unique reuse of the trusses.