The Interstate Bridge, as its bland official name goes, is in reality two parallel bridges. The eastern of the two was constructed originally in 1917. In face of increasing traffic, the second was added in 1958. Each of the two bridges has three lanes, and the structures also have a sidewalk for pedestrians and cyclists to cross the bridge on.

The bridges are becoming inadequate to carry the large traffic load of commuters going between the bedroom community of Vancouver, WA and jobs in Portland, OR and Washington County. While the possibility of adding a third bridge has been proposed, this is not a very practical idea as their is not a corresponding freeway infrastructure on the Portland side for the bridge to connect into. It has been hoped that MAX light rail would be expanded and extended across the Columbia to Vancouver, but in the past funding has failed to be approved by voters. However, I suspect that such a connection will be in place before 2010.