The Aerial Lift Bridge is a major landmark in the port city of Duluth, Minnesota. The span is a vertical lift bridge, which is rather uncommon, but it began life as an extremely rare transporter bridge—the first of just two such bridges ever constructed in the United States. Originally built in 1905, the bridge was upgraded in 1929–30 to the current lifting design and continues to operate today. The bridge was added to the National Register of Historic Places on May 22, 1973. A maritime museum maintained by the United States Army Corps of Engineers exists near the site of the bridge. The bridge spans the Duluth Ship Canal, which was put through the thin but long sand spit named Minnesota Point in 1870–71. The natural mouth of the St. Louis River is about seven miles farther southeast, and is split between Minnesota and Wisconsin. Creating this gap in the tiny peninsula meant that residents who lived on the new island needed to have a way to get across. Several different transportation methods were tried, though they were complicated by the weather. Ferries could work in the summer, but ice caused problems in colder months. A swinging footbridge was used, but was considered rather rickety and unsafe.
touristlink.com