Men from New France began to penetrate this rich fur country in the 17th cent.; in 1634, the French explorer Jean Nicolet became the first to enter the region. He was followed by explorers and traders—Radisson and Groseilliers, Duluth, La Salle, Jolliet, Perrot, and Cadillac—as well as by missionaries such as Jogues, Dablon, and Marquette. The Great Lakes region was controlled by a few widely scattered French posts, such as Kaskaskia, Vincennes, Prairie du Chien, and Green Bay; links were established between the Northwest settlements and those in French Louisiana (St. Louis, New Orleans). The two chief posts of the Old Northwest were Detroit and Mackinac (Michilimackinac), but French influence spread among the Native American groups east to the Iroquois country.
In the 18th cent. the Northwest was coveted not only by the British colonists in Canada, but also by those in the American seaboard colonies, who organized the Ohio Company in 1747 for the purpose of extending the Virginia settlements westward. At the same time, the French sought to strengthen their hold on the Northwest by building forts. The clash of British and French interests culminated in the expedition led by George Washington that resulted in the loss of Fort Necessity and the outbreak of the last of the French and Indian Wars. The wars ended in 1763 with the Treaty of Paris, by which the British obtained Canada and the Old Northwest.