The Third Ave. Bridge spans the Mississippi River in downtown Minneapolis and opened in 1918. The bridge is historically significant as an example of one of the first reinforced-concrete arch bridges over the Mississippi in the Twin Cities and also for its key role in connecting downtown with an emerging Northeast Minneapolis (or “East Bank” as it was referred to at the time). This page highlights the exciting history of the bridge planning, design, construction and legacy of the Third Ave. Bridge.
Historical timeline of the Third Ave. Bridge
An expanding Minneapolis
In the early 20th Century, Minneapolis was going through a period of expansion and population growth. The key downtown crossings of the river were the Hennepin Ave., 10th Ave. and Plymouth Ave. bridges. Before deciding on building the Third Ave. Bridge, city officials considered expanding the Hennepin Ave. Bridge or rebuilding the 1872 10th Ave. Bridge on either side. Just like engineers today, they counted traffic to make the case for a new bridge crossing. Political and design challenges delayed a decision several years.
The Third Ave. Bridge’s elegant reverse “S” curve was developed out of necessity, not aesthetics. In the initial designs, the bridge was to be located on a straight alignment above St. Anthony Falls, but there were concerns that the location could cause damage to the falls because of known weak shale spots in the riverbed. The chief designer for the Third Ave. Bridge was city engineer, Frederick Cappelen, a Norwegian engineer educated in Sweden and Germany who emigrated to the United States in 1880. He also designed the Franklin Ave. Bridge and Prospect Park Water Tower. Cappelen understood the foundation limitations and placed bridge pier locations to avoid dangerous breaks in limestone of the riverbed, which could cause a loss of the falls (and bridge).
Melan reinforced concrete
One of the reasons the bridge is historically significant is because it reflects the design and engineering of Josef Melan’s reinforcing system. A Melan Arch consists of a number of steel I-beams bent into an arch shape that are then covered in concrete. The bridge was designed and constructed using concrete, a bridge building material used in ancient times but modernized in the late 19th century. Melan’s concrete and steel reinforcement system blended the public’s trust in steel bridge building with the preferred aesthetics of the City Beautiful movement. Other bridges built during this time also were built out of reinforced concrete, including the Franklin Ave. Bridge and Fort Snelling-Mendota Bridge, and are associated with the City Beautiful Movement.
The bridge design includes several distinctive features, look through the pictures and captions below to learn more about them.
Construction of the bridge
Construction on the Third Ave. Bridge began in August 1914 by pouring the bridge’s eight piers. To work against the strong current of the falls, workers built steel-sheet cofferdams, an enclosure built in the water to aid in creating a dry area for construction. In 1915, timber falsework, which was used as a mold for the bridge arches, was placed. Crews then assembled the steel arches, constructed the forms, and poured the concrete creating the arch ribs. The crew re-used the same falsework for multiple arch ribs. From here, workers erected spandrels, the deck, railings, and light fixtures. The construction site itself included several systems to aid in the efficient construction of the bridge. See the infographic to learn more about construction methods used in 1914-1918.
The special collections of the Hennepin County Library and Minnesota Historical Society have several digital photograph collections of the construction and bridge over time. Additionally, MnDOT’s Historic Bridges website for the Third Ave. Bridge has technical reports available for reference. MnDOT is also currently drafting a National Register Nomination for the bridge to further preserve its legacy.