The Mackinac Bridge is a suspension bridge

Suspension bridge

A suspension bridge is a type of bridge in which the deck is hung below suspension cables on vertical suspenders. Outside Tibet and Bhutan, where the first examples of this type of bridge were built in the 15th century, this type of bridge dates from the early 19th century...

 spanning the Straits of Mackinac

Straits of Mackinac

The Straits of Mackinac is the strip of water that connects two of the Great Lakes, Lake Michigan and Lake Huron, and separates the Lower Peninsula of Michigan from the Upper Peninsula of Michigan. It is a shipping lane providing passage for raw materials and finished goods, connecting, for...

 to connect the non-contiguous Upper

Upper Peninsula of Michigan

The Upper Peninsula of Michigan is the northern of the two major land masses that make up the U.S. state of Michigan. It is commonly referred to as the Upper Peninsula, the U.P., or Upper Michigan. It is also known as the land "above the Bridge" linking the two peninsulas. The peninsula is bounded...

 and Lower

Lower Peninsula of Michigan

The Lower Peninsula of Michigan is the southern of the two major landmasses of the U.S. state of Michigan. It is surrounded by water on all sides except its southern border, which it shares with Ohio and Indiana. Geographically, the Lower Peninsula has a recognizable shape that many people...

 peninsulas of the U.S. state

U.S. state

A U.S. state is any one of the 50 federated states of the United States of America that share sovereignty with the federal government. Because of this shared sovereignty, an American is a citizen both of the federal entity and of his or her state of domicile. Four states use the official title of...

 of Michigan

Michigan

Michigan is a U.S. state located in the Great Lakes Region of the United States of America. The name Michigan is the French form of the Ojibwa word mishigamaa, meaning "large water" or "large lake"....

. Opened in 1957, the bridge (familiarly known as "Big Mac" and "Mighty Mac") is the third longest in total suspension in the world and the longest suspension bridge between anchorages in the Western hemisphere. The Mackinac Bridge carries Interstate 75

Interstate 75 in Michigan

Interstate 75 is a part of the Interstate Highway System and runs from Miami, Florida to Sault Ste. Marie in the Upper Peninsula of Michigan. I-75 enters the state from Ohio in the south, just to the north of Toledo. It runs generally north through Detroit, Pontiac and Bay City, crossing the...

 and the Lakes Michigan and Huron components of the Great Lakes Circle Tour

Great Lakes Circle Tour

The Great Lakes Circle Tour is a designated scenic road system connecting all of the Great Lakes and the St. Lawrence River. It consists of routes for circumnavigating the lakes, either individually or collectively.-Lake Superior Circle Tour:...

s across the straits and connects the city of St. Ignace

St. Ignace, Michigan

Saint Ignace, usually written as St. Ignace, is a city in the U.S. state of Michigan. As of the 2000 census, the city population was 2,678. It is the county seat of Mackinac County. From the Lower Peninsula, St. Ignace is the gateway to the Upper Peninsula.St...

 on the north end with the village of Mackinaw City

Mackinaw City, Michigan

Mackinaw City is a village in Emmet and Cheboygan counties in the U.S. state of Michigan. At the 2000 census the population was 859. The name "Mackinaw City" is a bit of a misnomer as it is actually a village...

 on the south.

Envisioned since the 1880s, the bridge was designed by engineer David B. Steinman

David B. Steinman

David Bernard Steinman was an American structural engineer. He was the designer of the Mackinac Bridge and many other notable bridges, and a published author. He grew up in New York City's lower Manhattan, and lived with the ambition of making his mark on the Brooklyn Bridge that he lived under...

 and completed in 1957 only after many decades of struggles to begin construction.
The bridge opened on November 1, 1957, ending decades of the two peninsulas being solely linked by ferries.