Mackinac (măk´Ĭnô´), historic region of the Old Northwest (see Northwest Territory), a shortening of Michilimackinac. The name, in the past, was variously applied to different areas: to Mackinac Island; to Michigan; to the whole fur-trading region supplied from the island; to the northern mainland shore (St. Ignace, Mich., has been sometimes called Ancient Michilimackinac); and to the southern mainland shore, where Mackinaw City, Mich. is located and where a fort called Old Mackinac once stood.

The Straits of Mackinac, a passage between the Upper and Lower peninsulas of Mich., connecting Lake Michigan and Lake Huron, served for many years as an important Native American gathering place. In 1634 the French explorer Jean Nicolet was the first European to pass through the straits. The French Jesuit Claude Allouez, in 1665, was the first missionary to go there; he was followed by Father Jacques Marquette, who established a mission at St. Ignace in 1671. A fort was later built there, and it became the headquarters of French trade operations in New France and an important military post in the Old Northwest; its importance declined when Detroit was founded in 1701.

The region passed into British hands in 1761 during the last conflict of the French and Indian Wars. In 1763 members of the British garrison at Old Mackinac were attacked and killed by the Ottawa during Pontiac's Rebellion. During the American Revolution, the fort and town at Old Mackinac, threatened by the exploits of the American general George Rogers Clark, were moved to Mackinac Island.

The island and the straits were awarded to the United States in 1783 by the Treaty of Paris, but they remained in British hands until 1794. One of the first events of the War of 1812 was the British capture of Mackinac; it was returned to U.S. control by the Treaty of Ghent in 1814. After the war, Mackinac Island became the center of operations of John Jacob Astor's American Fur Company, which thrived until the 1830s, when fur trading declined.

After the 1840s the straits area changed from an important crossroads to an out-of-the-way shipping point. Mackinac National Park, the second U.S. national park, was established on Mackinac Island in 1875, but it was turned over to the state along with the U.S. army post in 1895. Mackinac Island became a Michigan state park and, along with Bois Blanc Island, a popular summer resort.

Iron-ore mining revitalized the area in the early 20th cent., but the mineral was soon depleted. The Mackinac Straits Bridge (3,800 ft/1,158 m long; opened 1957) spans the straits and links St. Ignace with Mackinaw City. The connection has stimulated the economy of the Upper Peninsula as a result of the added transportation route for tourists, vacationers, and sports enthusiasts. The straits are an important link in the Great Lakes–St. Lawrence waterway.