The Mackinac Bridge, which spans the Straits of Mackinac, join together Michigan’s Upper and Lower peninsulas. Dubbed the Mighty Mac, the bridge stretches out for five miles, which includes its approaches, and is among the longest suspension bridges in the world.
   Construction of this toll bridge began in May 1954, and opened to traffic on Nov. 1, 1957. The total length of the suspension bridge, including anchorages, is 8,614 feet, with construction costs hovering around 100 million dollars. At mid-span, the roadway is approximately 200 feet above water level. Designed to accommodate changes in wind, temperature and weight, the deck at the center span could move as much as 35 feet to the east or west under severe wind conditions.
   Maintained by the Mackinac Bridge Authority, four lanes of Interstate 75 accommodate thousands of vehicles each day. Each year on Labor Day, two lanes of the bridge are closed to vehicle traffic for the annual Mackinac Bridge Walk. Walk-a-thon sponsors include the Mackinac Bridge Authority, the Upper Peninsula's St. Ignace Chamber of Commerce and the Lower Peninsula's Greater Mackinaw Area Chamber of Commerce.