Connecting Boston, Mass. With Northern New England. Photographed from Bunker Hill Monument. Cost $27,000,000,00. Largest bridge built in the United States since World War II. Over 2 miles long, double-decked with 3 lanes of one-way traffic on each level. Constructed on the site of North America's first ferry (1631). Main span was built by the American Bridge Company, subsidiary of the United States Steel Corporation.