Columbia River Interstate Bridge, Vancouver WA (#1492)

A fascinating set of twin bridges, connecting Portland, OR and Vancouver, WA. The first of the two bridges was built in 1917 as a single two-way bridge. Long before the Interstate highway system was named the bridge was named as the Interstate bridge simply for the fact that it connects two states, the bridges are now part of the Interstate system (I-5). Due to traffic demands, a second bridge that is a copy (more or less) of the first was opened in 1956 and each bridge was converted to being one-way. The first bridge was originally built as flat, but the new bridge was built with a hump so as to reduce the need for utilizing the lift section; after the new bridge was completed the old bridge was temporarily shut so as to be modified to have the same hump. Both bridges are now considered to be functionally obsolete, but attempts to replace them have been complicated by multiple factors including their proximity upriver to Portland International Airport and downriver to a railroad bridge.

The Wikipedia on the bridge includes interesting details and photos: en.wikipedia.org/wiki/Interstate_Bridge

Interesting photos of the construction of the original portion are in a Google Ebook: books.google.com/books?id=NdENAAAAYAAJ&printsec=frontcover&source=gbs_ge_summary_r&cad=0#v=onepage&q&f=false