Michigan's two peninsulas are separated by the four-mile-wide Straits of Mackinac*, which is the body of water that connects Lake Michigan and Lake Huron. In the 19th century passenger ferries transported people between the Upper and Lower Peninsulas, and in the 1920s, the state implemented car ferries so that people could get their automobiles across the Straits. Immediately there was great demand for this service, and soon there were reports that the lines of cars waiting to board would sometimes be backed up as much as 15 miles! Clearly there was a need for a bridge. This represented a monumental challenge, in terms of both engineering and expense. But in November 1957, the new Mackinac Bridge opened to traffic. At the time it was the costliest stretch of road in the world, and it remains one of the longest suspension bridges in the world.
*Pronounced MACK-ih-naw. Some locations spell it more phonetically - such as Mackinaw City - but both spellings are pronounced the same. The word is a French corruption of an Ojibwa name for a division of their tribe, early inhabitants of the area.
The websitemackinacbridge.orghas lots more information, history, facts, and figures about the Bridge itself... but the focus of this page is the Mackinac Bridge Dedication Festival, which took place the following summer.