Ross Island Bridge, Spanning Willamette River at Powell Boulevard, Portland, Multnomah County, OR
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Significance: The Ross Island Bridge is one in an ensemble of twelve monumental highway bridges across the lower Willamette River. It is one of five Portland spans (with Burnside, Sellwood, Lovejoy Viaduct, and the Broadway Bridge) associated with Gustav Lindenthal during the period 1924-1928. The Portland bridges were the last of this master engineer's career, with Ross Island a rare example of a Lindenthal highway-only deck truss. In Oregon, Ross Island is also: 1) one of 215 known highway truss bridges of any type or age surviving; 2) one of seven known cantilever highway trusses; 3) the only known cantilever highway deck truss, made further unique among cantilever trusses because it was designed without a suspended center span, thereby incorrectly appearing to be an arch bridge. Ross Island is also significant because of its unusually finely subdivided Warren truss side spans. Created almost exclusively for motor vehicles, Ross Island was the first fixed-span (designed not to raise for river traffic) Willamette River bridge in downtown Portland, and was the first river bridge in the central city's history to be designed without trolley tracks.
Survey number: HAER OR-102
Building/structure dates: 1926