Connecting the Upper and Lower Peninsulas of the state of Michigan in the US is the Mackinac Bridge. It spans the Straits of Mackinaw, a waterway between the locales of St. Ignace, MI on the north end with Mackinaw City, MI on the south end of the bridge. Familiarly known as 'Big Mac' and 'Mighty Mac', this suspension bridge was opened in 1957.

As of 2019, it is the longest suspension bridge between anchorages in the Western Hemisphere. It's length is slightly less than 5 miles (4.995 mi or 8,038 km) with a towering height of 552 ft (168 m). The 'Big Mac' was designed by David B. Steinman, an American civil engineer, who also designed bridges in many other countries during his lifetime.

Total cost for construction of the bridge in 1957 was $95 million USD, equivalent to $726 million in 2018. Today, the 'Mighty Mac' is a toll bridge for passenger vehicles ($4.00) and trucks ($5.00).

Since 1958, on Labor Day, a national holiday celebrated on the first Monday in September, the bridge is open to walkers. Walkers are led across by the governor of Michigan with an estimated 40,000 to 65,00 people participating in the five-mile walk. The record number of walkers was estimated at 85,000 in 1992 when President George H. W. bush crossed the 'Mighty Mac'.

Starting in 2017, all vehicular traffic on the bridge as well as shipping and boating below, is stopped for the duration of the event. This walk is the sole exception to the rule prohibiting pedestrians on the bridge.

More Info: en.wikipedia.org