Built by the Northern Pacific Railroad Company from 1880-1883, the rail bridge represents the unprecedented industrial expansion of its era. As the first bridge to span the upper Missouri River, it contributed significantly to the growth of the rail roads, now known to be one of the greatest infrastructure projects in American history.
It is of note that the bridge was designed by engineer George Shattuck Morison, a leading bridge designer of his time. Throughout his career, Morison oversaw the construction of bridges over many of America's great waterways. He designed 5 bridges across the Mississippi, 10 across the Missouri, and many smaller bridge projects. Given the engineering challenges he overcame to connect the vast expanses of the American West, Morison's contribution to the history of the United States stands without question.
Piers 2 and 3 of the bridge, which lie within the river channel, were constructed using pneumatic caissons. This technique involved floating a hollow metal cylinder into place, and sinking it down into the mud. Once in contact with the river bottom, pumps were used to pressurize the chamber. Laborers would work in a dim, air tight environment clearing the river bottom soils. As this was cleared, this would allow the caisson to further sink. This was continued until bedrock of sufficient stability to maintain the pier was reached. The figure above shows workers in the caisson used to construct pier 2.