Aerial Lift Bridge | |
 The Aerial Lift Bridge inDuluth, MN | |
  Location in United States Show map of the United States | |
| Location | Lake Avenue,Duluth, Minn. |
|---|---|
| Coordinates | 46°46′44.5″N92°5′33.9″W / 46.779028°N 92.092750°W /46.779028; -92.092750 |
| Built | 1905, reconstructed in 1929 |
| Architect | Thomas F. McGilvray;C.A.P. Turner |
| NRHP reference No. | 73002174[1] |
| Added to NRHP | May 22, 1973 |
TheAerial Lift Bridge, earlier known as theAerial Bridge orAerial Ferry Bridge, is a landmark in the port city ofDuluth, Minnesota. The span began life in 1905 as the United States' firsttransporter bridge: Only one other was ever constructed in the country,the Sky Ride inChicago.[2] The span was converted in 1929–1930 to avertical-lift bridge, also rather uncommon, although there are six such bridges along Ontario'sWelland Canal. It remains in operation. The bridge is owned and operated by the City of Duluth. The bridge was added to theNational Register of Historic Places on May 22, 1973. TheUnited States Army Corps of Engineers maintains a nearby maritime museum.
The bridge spans theDuluth Ship Canal, which was put through the miles-longsand spit namedMinnesota Point – commonly called Park Point by locals – in 1870–1871. The natural mouth of theSaint Louis River is about seven miles (11 km) farther southeast, and is split betweenMinnesota andWisconsin. Creating this gap in the sand spit meant that residents who lived on the new island needed to have a way to get across. Several 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.
In 1892, a contest was held to find a solution. The winning design came from John Low Waddell, who drew up plans for a high-rise vertical lift bridge. The city of Duluth was eager to build the bridge, which would have been about 130 feet (40 m) wide. However, theWar Department objected to the design, and the project was canceled before it could be built. Waddell's design went on to be built inChicago, Illinois, as the slightly larger South Halsted Street Bridge, which was removed in 1932.[3][4][5]
New plans were later drawn up for a structure that would ferry people from one side to the other. This type of span, known variously as an aerial transfer, ferry, or transporter bridge, was first demonstrated inBilbao'sVizcaya Bridge in 1893 and in France in 1898. Duluth's bridge was inspired by the one in France, though the actual construction is quite different. Thearchitect was a city engineer, Thomas McGilvray.[1]
When it was completed in 1905, the Aerial Bridge's gondola had a capacity of 60 shorttons (54tonnes) 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.[6] 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 firm finally commissioned to design the new bridge was the descendant of Waddell's company. The new design, which closely resembles the 1892 concept, is attributed toC.A.P. Turner. Reconstruction began in 1929.[1] 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 newcounterweights to balance the weight of the lifting portion. The new bridge was first lifted for a vessel, the U.S. Army Corps of Engineers tugboatEssayons, on March 29, 1930.[6][7]
The bridge can be raised to its full height of 135 feet (41 meters) in about a minute, and is raised about 5,000 times per year.[8] The span is about 390 feet (120 meters). As ships pass, there is a customary horn-blowing sequence that is copied back. The bridge's "horn" is made up of twoWestinghouse Airbrake locomotive horns.[9] Long-short-short is known as the Captain's Salute and is the most common of the ship signal exchanges. On November 10, the anniversary of the sinking of theSS Edmund Fitzgerald with all hands inLake Superior, the Lift Bridge exchanges a special salute with theSS Arthur M. Anderson as it comes into Duluth Harbor. The salute is given in honor of theFitzgerald and her crew; theAnderson was the last lake freighter to have contact with theFitzgerald before it went down, and was the first vessel on scene to search in vain for survivors. The exchange is known as the Master Salute consisting of the horn sequence of long-long-long-short-short.[citation needed]
The bridge was designated as aNational Historic Civil Engineering Landmark by theAmerican Society of Civil Engineers in 2017.[10]
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Crossings of theSaint Louis River | ||||
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