Jefferson County is located in south central Illinois, and it holds the intersection of Interstates 57 and 64.
It lies about one hour north of Carbondale, five hours south of Chicago, one and a half hours east of St. Louis, and one and a half hours west of Evansville, Indiana.
Its county seat is Mt. Vernon.
The adjacent counties are: Marion (north), Washington (west), Franklin (south), and Wayne (east).
Click here for one SCIGP member's views about Jefferson County politics.