Plans for a bridge connecting Delaware to New Jersey had been around since the 1920s, but opposition from shipping interests and the Navy prevented the project from gaining momentum until the 1940s. Construction began on the first bridge in 1949 and was opened in 1951. The bridge measures 2150 feet long with the roadway suspended 188 feet above waterline to provide clearance for large ocean going vessels. A second span was constructed in 1964 to relieve growing congestion at the crossing. The bridges are the world's longest twin suspension bridges.

http://www.phillyroads.com/crossings/delaware-memorial/