November 28, 1949: A view from the Charlestown end of the new Mystic River Bridge showed the double deck construction, with separate levels for incoming and outgoing traffic. The new Mystic River Bridge is New England's largest, longest structure of that type. It is 2700 feet longer than San Francisco's famed Golden Gate , and is twice as long as New York's Brooklyn Bridge. The War Department set 135 feet above mean tide as the necessary clearance for the big ocean-going shipping which makes much use of the Mystic River. The length of 2 1/4 miles was necessary to maintain grades of about 3 percent and not to exceed 6 percent. A shorter bridge would have plunged down on each side like a roller coaster.