Sixth Street Viaduct, Spanning Burlington Northern Railroad & Valley Street, Burlington, Des Moines County, IA

Significance: The Sixth Street Viaduct is actually comprised of two separate structures: a pin-connected Pratt truss built over the tracks of the Chicago, Burlington and Quincy Railroad in 1886 and a girder overpass that was built as an approach in 1903-04. Both bridges are technologically significant as rare survivors of their type. The 1886 span is one of only three pinned through trusses remaining in Iowa's urban areas. Similarly, the open-web design of the 1903 girders is the only example of this uncommon configuration known to remain in the state. The viaduct as a whole is historically significant for its role in the development of downtown Burlington and its representation of the sometimes uneasy relationship between the city and the railroad that supported it.
Survey number: HAER IA-36
Building/structure dates: 1886 Initial Construction
Building/structure dates: 1903- 1904 Subsequent Work