French explorers Jacques Marquette and Louis Jolliet explored the Illinois River in 1673. Marquette soon after founded a mission at the Grand Village of the Illinois in Illinois Country. In 1680, French explorers under René-Robert Cavelier, Sieur de La Salle and Henri de Tonti constructed a fort at the site of present-day Peoria, and in 1682, a fort atop Starved Rock in today’s Starved Rock State Park. French Empire Canadiens came south to settle particularly along the Mississippi River, and Illinois was part of first New France and then of La Louisiane until 1763, when it passed to the British with their defeat of France in the Seven Years’ War.
The British Crown made the region of Illinois part of the territory reserved for Indians west of the Appalachians, and then part of the British Province of Quebec. In 1778, George Rogers Clark claimed Illinois County for Virginia. In a compromise, Virginia ceded the area to the new United States in 1783 and it became part of the Northwest Territory, to be administered by the federal government and later organized as states. Connecticut ceded northern Illinois in 1786 (see Connecticut Western Reserve).