[citation needed] In 1673, Jesuit Father Jacques Marquette and French-Canadian explorer Louis Jolliet became the first Europeans known to have descended the Mississippi River.
Descending the Mississippi, in June, they met the Peoria and Moingwena bands of Illinois at the Haas/Hagerman Site near the mouth of the Des Moines River in Clark County, northeastern Missouri.
Kaskaskia became the capital of Upper Louisiana, and a larger Fort de Chartres was built in 1718, nearby North close to Prairie du Rocher.
In the same year, the French imported African slaves from Saint-Domingue (Santo Domingo) to work in the lead mines.
A visitor, writing of Kaskaskia about 1715, said that the village consisted of 400 Illinois men, "very good people," two Jesuit missionaries, and "about twenty French voyageurs who have settled there and married Indian women.
One devout Roman Catholic full-blooded Indian woman disowned her half-breed son for living "among the savage nations.
[8] Male descendants of the French, Indians, and mixed bloods at Kaskaskia became the voyageurs and coureurs des bois who would explore and exploit the Missouri River country.
French goals stimulated the expedition of Claude Charles Du Tisne to establish trade relations with the Plains Indians in 1719.
Contemporary historians believe the greatest fatalities during this period were due to new infectious diseases, to which the Native Americans had no immunity.
The Ottawa, Sauk, Fox, Miami, Kickapoo and Potawatomi devastated the Illiniwek and occupied their old tribal range along the Illinois River.
[10] On July 4, 1778, during the American Revolutionary War, George Rogers Clark captured the town and Fort Gage.