The bridge at Vantage was the seventh bridge to be built across the Columbia River. Including approaches, it was half a mile long. The bridge consisted of a Pratt through truss (the truss -- the steel framework -- was cross-braced above and below traffic). The top and bottom chords of the truss were sloped. It was a cantilever bridge, one in which the center spans extend out from their end-supports. At center, the bridge cleared the water by 70 feet, allowing large ships to navigate beneath it.
The 1927 Vantage Bridge was the first bridge in Washington that workers constructed by working in pressurized caissons sunk 70 feet under the riverbed. The workers entered the caissons through air locks. The pressure within the caissons was so great that some of the workers became seriously ill from its effects.
The Vantage Bridge was one of four cantilever bridges constructed across the Columbia during the 1920s. It carried the Sunset Highway, a mostly gravel road which was at the time the state’s main east-west thoroughfare. Eventually the Sunset Highway was completely paved, greatly increasing speed and safety and decreasing wear and tear on the early automobiles that traveled it.
The Vantage Bridge served motorists until 1962, when a higher bridge was constructed over the reservoir created by the Wanapum Dam, which began operation in 1964. The old Vantage Bridge was put into storage. In 1968 it was rebuilt to cross the Snake River at Lyons Ferry and it is now (2005) the oldest extant steel cantilever bridge in the state.