Saint Louis County
St. Louis County is a county located within the far eastern portion of Missouri. It shares borders with the Mississippi River, the Missouri River, the Meramec River, and the state of Illinois. As of the 2015 Census Bureau population estimate, the population was 1,003,362,making it the most populous county in Missouri. Its county seat is Clayton.
St. Louis County borders but does not include St. Louis, which is an independent city. It is included in the St. Louis, MO-IL Metropolitan Statistical Area.
The Missouri River forms the northern border with St. Charles County, exclusive of a few areas where the river has changed its course. The Meramec River forms most of its southern border with Jefferson County. To the east is the City of St. Louis and the Mississippi River. The western boundary with Franklin County is the north-south line where the distance between the Meramec and Missouri Rivers is the shortest, bisecting the City of Pacific roughly 2 blocks east of Hwy OO/F (First street).