St. Louis County, Missouri

Saint Louis County (typically abbreviated as St. Louis County) is a county bordering on the Missouri and Mississippi Rivers in eastern Missouri. It is named for, but does not include, the city of St. Louis, which lies directly to its east. Clayton is the county seat, and Florissant is the largest city. It had a population of 998,954 at the 2010 census, making it the largest county in Missouri and the 40th-largest county in the United States by population.

One of the state's five original counties, the jurisdiction has existed since 1812, and has been separate from St. Louis City since 1877, when the city voted to withdraw from the county and become an independent city. Since the mid-20th century, it has been heavily suburban in character and is now significantly more populous than St. Louis itself. It is the most significant part of the St. Louis metropolitan area.

The county is roughly divided into three areas: North County (the part north and east of Interstate 70), South County (the part south and east of Interstate 44) and West County (the part between 70 and 44, which is the most populous).

History

Prior to European settlement, the greater St. Louis area was dominated by a succession of Native American cultures, most notably the Mississippian culture from around 900 to 1500 AD. The most notable evidence they left behind was the large number of earthen mounds that dotted this part of the Mississippi Valley.

The first instance of European exploration was the expedition of Jacques Marquette and Louis Joliet in 1673, as they sailed down the Mississippi River on behalf of France. The French explorer Robert-Cavalier de La Salle followed in 1682, formally claiming the entire region on behalf of his country and giving it the name of "Louisiana."

Although a few outposts were established on the east bank of the Mississippi in the early 18th century, settlement in the St. Louis area did not begin until 1764, when the city of St. Louis was itself laid out as a trading post by Pierre Laclède and Auguste Chouteau (by which time all of Louisiana west of the river had been ceded to Spain). Though it would remain the largest and most prominent of the fledgling communities in the region, others soon followed--Carondelet in 1767 (later annexed to St. Louis), and St. Ferdinand (later Florissant) sometime between 1772 and 1786. Further west, Creve Coeur appears to have existed sometime before 1796.

By the time of the Louisiana Purchase, the Spanish colonial authorities had subdivided the Louisiana Territory into districts, with the area immediately south of the lower Missouri River being included in the district of St. Louis (named for the city). Following the handover to the Americans, these districts were generally retained, and when the Missouri Territory was organized on October 1, 1812, the St. Louis district became one of the future state's five original counties (the others being Cape Girardeau, New Madrid, St. Charles, and Ste. Genevieve).