Jefferson County

I-55 South / SR-21

Jefferson County, the southern MSA county along I-55, anchored by Arnold (the county's largest city, directly south of St. Louis County), Imperial, Barnhart, Festus, Crystal City, Herculaneum, Pevely, De Soto, and Hillsboro (the county seat). Jefferson County offers more affordable housing than the St. Louis County suburbs while providing practical commuting distance to St. Louis employment centers.