St Louis County

County in east-central Missouri; area 1,311 sq km/506 sq mi; population (1990) 993,500. Its capital is Clayton. It does not include the independent city of St Louis, but lies directly to the south, west, and east of it, constitutes the largest part of its metropolitan area, and contains most of its residential suburbs. Wheat and corn are grown and dairy cattle are raised in the few agricultural pockets that remain along the county's perimeter. There is also some manufacturing and business development.

The county is bounded to the east by the Mississippi River, to the northwest by the Missouri River, and to the southeast and southwest by the Meramec River. In the west there are a number of parks and nature reserves that maintain the bluffs and other features of the original landscape.