Illinois Country

The Illinois Country (French: Pays des Illinois [pɛ.i dez‿i.ji.nwa]; lit. '"land of the Illinois (plural)"', i.e. the Illinois people) (Spanish: País de los ilinueses) — sometimes referred to as Upper Louisiana (French: Haute-Louisiane [ot.lwi.zjan]; Spanish: Alta Luisiana)—was a vast region of New France claimed in the 1600s in what is now the Midwestern United States. While those names generally referred to the entire Upper Mississippi River watershed, French colonial settlement was concentrated along the Mississippi and Illinois Rivers in what is now the U.S. states of Illinois and Missouri, with outposts on the Wabash River in Indiana. Explored in 1673 from Green Bay to the Arkansas River by the Canadien expedition of Louis Jolliet and Jacques Marquette, the area was claimed by France. It was settled primarily from the Pays d'en Haut in the context of the fur trade, and in the establishment of missions from Canada by French Catholic religious orders. Over time, the fur trade took some French to the far reaches of the Rocky Mountains, especially along the branches of the broad Missouri River valley. The French name, Pays des Ilinois, means "Land of the Illinois [plural]" and is a reference to the Illinois Confederation, a group of related Algonquian native peoples.

The Illinois Country was governed from the French province of Canada until 1717 when, by order of King Louis XV, it was annexed to the French province of Louisiana, becoming known as "Upper Louisiana". By the mid-18th century, major settlements included Cahokia, Kaskaskia, Chartres, Saint Philippe, and Prairie du Rocher, all on the east side of the Mississippi in present-day Illinois; and Ste. Genevieve across the river in Missouri, as well as Fort Vincennes in what is now Indiana.

As a consequence of the French defeat in the French and Indian War in 1764, the Illinois Country east of the Mississippi River was ceded to the British and became part of the British Province of Quebec; the land west of the river was ceded to the Spanish (Luisiana).

During the American Revolutionary War, Virginian George Rogers Clark led the Illinois campaign against the British. Illinois Country east of the Mississippi River along with what was then much of Ohio Country became part of Illinois County, Virginia, claimed by right of conquest. The county was abolished in 1782. In 1784, Virginia ceded its claims. Part of the area was incorporated in the Northwest Territory. The name lived on as Illinois Territory between 1809 and 1818, and as the State of Illinois after its admission to the union in 1818. The residual part of Illinois Country west of the Mississippi was acquired by the United States in the Louisiana Purchase in 1803.