This bridge was originally built in 1905 as a transporter bridge. The transporter bridge was designed by Thomas McGilvray of Duluth, Minnesota. In 1930, noted engineer Claude Allen Porter Turner proposed a redesign of the structure to convert it into a traditional vertical lift bridge. The proposed lift span was designed by a firm with a long history in lift design, Harrington, Howard & Ash. This firm was formerly associated with famous enginer J. A. L. Waddell, who had originally proposed a lift bridge at Duluth in 1892, but which was rejected by the War Department, resulting in the transporter bridge being built instead. One unusual (but fortunate from a preservation perspective) aspect of the 1930 conversion to a lift bridge is that the original transporter truss span between the top of the towers was not simply demolished as one might expect. Rather, it was raised up by adding steel to the top of the original towers, which provided room for the new lifting truss span to raise fully for boats. It is possible that the original transporter towers were not stiff enough to be freestanding, which would account for why the transporter truss was spared demolition, as it would stiffen and brace the two towers. In any case, the bridge today has a unique appearance among lift bridges since it has two truss spans: the moving lift truss span from 1930, and the original 1905 transporter truss on top. As such, although the bridge no longer functions as a transporter bridge, it retains most of the original material of the 1905 transporter bridge with the exception of the gondola. The bridge is historically significant thus as both a notable vertical lift bridge and also as a remanant of the only transporter bridge surviving in the United States.
Above: Historical photo showing bridge as originally designed.
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