The county was first visited by white colonists when missionary priests, Illinois French, and Kaskaskia and Tamaroa Indians settled the temporary village of Des Peres, 1700-03. The village site, laid out 18 years after La Salle claimed the territory for France, is now within St. Louis city limits.
The county's first permanent settlement was St. Louis, founded by Pierre Laclede, 1764. Though France had ceded the region to Spain, 1762, the settlements were made French, and other early villages were Creve Coeur, Carondelet, and Florissant, and early Catholic educational center. In the late 1700's, Americans began to settle farms on the creeks and rivers. On Cold Water Creek, a Methodist Church was formed, 1806, and on Fee Fee Creek a Baptist, 1807.
St. Louis and its surrounding settlements formed one of 5 Spanish districts before the American period began, 1804, and one of first 5 counties of Missouri Territory, organized, 1812. St. Louis city and county separated, 1876, and Clayton was laid out as the new county seat, 1878. The name is for Ralph Clayton, who gave 100 acres of land.
St. Louis County developed as a suburban and recreational area and a feature of its growth is the incorporated towns founded outside the city limits of St. Louis.
Events of early county history include the establishment
of Ft. Prince Charles at the mouth of the Missouri by the Spanish, 1767, and the building of Ft. Bellefontaine a few miles from the river's mouth by the U.S., 1805. Indian trading post and military cantonment, Bellefontaine was one of the first American forts west of the Mississippi. Zebulon M. Pike left from Bellefontaine on his great expedition to the Southwest, 1806.
Points of interest are Jefferson Barracks, dating from 1826; National Cemetery; log cabin home of Ulysses S. and Julia Dent Grant; Rockwoods Reservation; Babler State Park; Concordia Historical Institute Museum; Museum of Transport; and Lambert-St. Louis Airport. In the county are the major part of Washington University; Eden (Reformed Evangelical) Seminary; Concordia (Lutheran) Seminary; Catholic seminaries of Kenrick, St. Stanislaus, and Holy Family, and colleges of Fontbonne, Chaminade, and Webster.