Rainbow Arch Bridge

Rainbow Arch Bridge. . Spanning the South Platte River, the Rainbow Arch Bridge carried vehicular traffic from its completion in 1923 until its closure in 1988. Engineer James B. Marsh of Des Moines, Iowa, designed the structure in 1922. Denver bridge contractor Charles G. Sheely built it in 1922-23 for just over $69,000. With its eleven 90-foot concrete arches, the bridge extended over 1,100 feet. A year after it was finished, light standards were installed that linked the bridge visually with Fort Morgan's Main Street.

For the Rainbow Arch Bridge, Marsh used a design that he had patented in 1912. Marsh's invention was an ingenious blend of steel and concrete technologies, which combined the concrete arch form with a sophisticated steel reinforcing system. The reinforcing was so heavy and complex, in fact, that his bridges have been called steel structures with concrete veneers. Marsh built several small-scale and medium-scale rainbow arches throughout the Midwest in the 1910s. This bridge at Fort Morgan represented the first large-scale application of his distinctive design.

The bridge at Fort Morgan has been listed on the National Register of Historic Places. It is the only rainbow arch built in Colorado, and at its completion it was the longest rainbow arch in the world. It is today a nationally significant example of the important, but relatively uncommon, structural type. As it arches gracefully over the broad Platte River, the Rainbow Arch Bridge symbolizes the permanence of early highway construction in the state.