The Aerial Lift Bridge is a landmark in Duluth. It is one of Minnesota’s most recognizable attractions. The bridge began 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 a vertical lift bridge and continues to operate today. The bridge was added to the National Register of Historic Places in May, 1973.
The bridge spans the Duluth Ship Canal, which was put through the thin but long sand spit named Park Point in 1870–71. 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.
New plans were drawn up for a structure that would ferry people from one side to the other. This type of span, which is known variously as an aerial transfer, ferry, or transporter bridge, was first demonstrated in Bilbao‘s Vizcaya Bridge in 1893 and one in France in 1898. Duluth’s bridge was inspired by the one in France, though the actual construction is quite different. The architect was a city engineer, Thomas McGilvray.
When it was completed in 1905, the Aerial Bridge’s gondola had a capacity of 60 short tons (54 tonne) and could carry 350 people plus wagons, streetcars, or automobiles. A trip across the canal took about one minute, and the ferry car moved across once every five minutes during busy times of the day. A growing population on Minnesota Point, a greater demand for cars, and an increase in tourism soon meant that the bridge’s capacity was being stretched to the limit.
A remodeling was planned that would remove the gondola and incorporate a lifting platform into the structure. The new design, which closely resembles the 1892 concept, is attributed to C.A.P. Turner. Reconstruction began in 1929. In order to ensure that tall ships could still pass under the bridge, the top span had to be raised to accommodate the new deck when raised. The support columns on either side were also modified so that they could hold new counterweights to balance the weight of the lifting portion. The new bridge first lifted for a vessel on March 29, 1930.
The bridge can be raised to its full height of 135 feet in about a minute, and is raised approximately five thousand times per year. The span is about 390 feet. As ships pass, there is a customary horn-blowing sequence that is copied back. The bridge’s “horn” is actually made up of two Westinghouse Airbrake train whistles. Long-short-long-short means to raise the bridge, and Long-short-short is a friendly salute.
The bridge was freshly painted in 2012. You can watch the bridge go up from some of the city side rooms at the hotel.