St. Charles Air Line Bridge, Spanning South Branch of Chicago River, north of Sixteenth Street, Chicago, Cook County, IL

Significance: Like all Strauss heel-trunnion bascule bridges, the St. Charles Air Line Bridge rotates vertically, lifting to clear the river it spans. This particular bridge is unique, however, in that its design anticipated a one-time horizontal movement - to a new, straighter channel of the Chicago River. Its original 260'-0" leaf exceeded the previous world record by 30'-0", but was shortened by 40'-0" during the move. The bridge represents Strauss' first use of air-buffered pistons on the operating struts. It is also significant for the railroad it carries, an unusual "gentlemen's agreement" between four of Chicago's earliest railroads.
Unprocessed Field note material exists for this structure: N650
Unprocessed Field note material exists for this structure: N966
Survey number: HAER IL-157
Building/structure dates: 1917-1919 Initial Construction
Building/structure dates: 1930 Subsequent Work