Jefferson County Flag

Jefferson County

State:
Illinois
County Seat:
Mount Vernon

Jefferson County's estimated 2025 population is 36,122 with a growth rate of -0.27% in the past year according to the most recent United States census data. Jefferson County is the 38th largest county in Illinois. The 2010 population was 38,757 and has seen a growth of -6.8% since that time.

36,122
Total Population
63
Population Density (mi²)
38
Population Rank (State)
-99 -0.27%
Annual Population Growth

Jefferson County Population

Demographics

Economics and Income Statistics