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.