The MBA was authorized in 1952 to sell bonds to finance construction, which were sold on December 17, 1953, to finance the $99.8 million (equivalent to $ in ) cost of the bridge. The structure was designed by David B. Steinman and built by Merritt-Chapman & Scott for the substructure and the American Bridge Company division of U.S. Steel Corporation for the superstructure. Construction started in 1954 and the Mackinac Bridge opened to traffic on November 1, 1957. Final work on the bridge was completed in September 1958. Overall, the structure has a central suspension span flanked by two side spans. With the two backstay spans, the Mackinac Bridge is long between cable anchorages, the longest in the world at the time it opened. The total length of the structure is with two towers and of clearance for passing ships under the main span. In 2000, the bridge was named "Michigan's No. 1 Civil Engineering Project of the 20th Century" by the Michigan Section of the American Society of Civil Engineers (ASCE), and the structure was named a National Historic Civil Engineering Landmark in 2010 by the national ASCE.