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Plymouth

Upper (First Plymouth Avenue) Bridge (1873-1886)

Engineering for this bridge type

The city of St. Anthony, on the east bank of the river, was incorporated earlier than Minneapolis and took an early lead in population and industrial development. However, by the late 1860s, Minneapolis had outstripped St. Anthony in growth, with an 1870 population of 13,066 in comparison to St. Anthony’s 5,013. On April 9, 1872, the two cities consolidated under the name of Minneapolis. As a condition of the merger, Minneapolis agreed to build two new bridges across the Mississippi River, one above and one below the Hennepin Avenue suspension bridge. In November 1873, the Upper Bridge was completed, linking Thirteenth Avenue (today’s Plymouth Avenue) on the west side with 8th Avenue NE on the east side.

Second Plymouth Avenue Bridge (1886-1983)

Engineering for this bridge type

The second Plymouth Avenue bridge, an iron truss structure, was built in 1886, with a major remodeling in 1913. In 1952, it was raised by sixteen feet to increase clearance for river navigation. Cross-river travel at this location came to a temporary halt in 1981 when the bridge was closed due to the rusty and unsafe condition of the floor beams.

  
  Looking north at the Boom Island and southern Bassett's Creek areas in about 1904. The bridge in the center is the Plymouth Avenue Bridge with the Broadway Bridge and a Northern Pacific Railroad bridge to the north. Note the large stacks of lumber and the numerous steam-powered sawmills along the river.
 
  Third Plymouth Avenue Bridge (1983-present)

Engineering for this bridge type

The latest Plymouth Avenue bridge employs bridge technology which was revolutionary for its time and is still quite unusual. It is built from a series of cantilevered concrete box girders, which allows faster construction without the need for wooden falsework to hold the bridge until it can support itself. Embedded in the concrete are stranded, tensioned cables which strengthen the material and resist salt corrosion. This represents the only bridge using this construction method in the state of Minnesota.