The Mackinac bridge is a bridge that connects Michigan's upper and lower peninsulas. The city of Saint Ignace is at the north end of the bridge, in the upper peninsula, while Mackinac city is on the south side of the bridge, in the lower peninsula. Before the construction of the Mackinac bridge, the only way to cross from one of Michigan's peninsulas to the the other was by boat. Interstate 75, which runs from Florida into the upper peninsula of Michigan, crosses the bridge to reach the upper peninsula. The total span of the bridge, including the lead-up on the shore, is nearly 5 miles (slightly more than 8 kilometers).
The areas surrounding the Mackinac bridge and the route connecting the upper and lower peninsulas became very important to trade and tourism in the 19th and 20th centuries. Before the bridge was built, car ferries sometimes carried thousands of cars across the Straits of Mackinac each day. This was, however, insufficient to meet the traffic demands, and there were often long traffic backups. By the 1880s, people were beginning to discuss the idea of constructing a bridge.
Despite the perceived necessity for a bridge, disagreements and financial issues delayed the beginning of construction greatly. The actual construction of the Mackinac bridge did not begin until 1954. Work was not performed on the Mackinac bridge during Michigan's harsh winters, and construction took roughly three and a half years. In November of 1957, the bridge was opened to traffic and the ferry service was stopped. Roughly $100 million US Dollars were spent on the construction of the bridge and five workers died during the process.
The Mackinac bridge was, out of necessity, built to withstand relatively extreme conditions. High winds are common through the Mackinac straits, so the bridge is able to swing a great distance in either direction before losing any structural integrity. It was also built to withstand changing temperatures. Michigan winters regularly drop far below freezing while summer temperatures commonly reach and exceed 85°F (about 30°C).
Though the Mackinac bridge was constructed for practical purposes, it has become a tourist destination in and of itself, as it is one of the world's largest suspension bridges. Each year, an event known as the "Mackinac Bridge Walk" occurs in which people, led by Michigan's governor, walk across the bridge. The bridge is not open for walking or biking during the rest of the year, though people can pay to have themselves and their bikes driven across.
