Census 2000 showed Jefferson County’s population as 198,099. The 2004 MO estimate was more than 210,000, a 6.21% increase. Jefferson County limits extend over 664 square miles of land, lying west and south of the city of St. Louis. The mammoth Mississippi River borders Jefferson County to the east, affording splendid views to the sub-divisions and towns found there.

People from densely populated Saint Louis County and the city of St. Louis have migrated into Jefferson in the past three decades, as the county experiences residential and industrial growth. Manufacturing ranks as a major industry of Jefferson County, though it used to be primarily agricultural. Today, the southern and eastern sections of Jefferson County remain sparsely populated, with large family farms scattered through the land.

A total of 31 communities comprise Jefferson County, 13 of which are incorporated. The county seat is Hillsboro, population 2,805. Found here is Jefferson College, the only college within Jefferson County limits. The largest community is Arnold, home to more than 20,000. Situated on the Interstate 55 corridor only 20 miles south of St. Louis, Arnold is a thriving city. Nestling on the banks where the Meramec River meets the Mississippi, Arnold offers scenic beauty along with a prime business locale.

The next largest city in Jefferson County is Festus, with just under 10,000 residents. Known as a progressive city, Festus is home to the rock group known as the Bottle Rockets. The town of De Soto, population 6,375, rests peacefully in the beginning peaks of the Ozark Mountain Range, in Jefferson County’s southeastern corner. Some other communities in Jefferson County include Byrnes Mill, Crystal City, Herculaneum and Pevely, all with populations less than 5,000. Pevely is the site of the exciting I-55 Raceway.