Jefferson County, Illinois

Jefferson County is a county located in the southern part of the U.S. state of Illinois. According to the 2020 census, it has a population of 37,113. The county... Wikipedia

• Founded:  1819
• Named for:  Thomas Jefferson
• Seat:  Mount Vernon
• Largest city:  Mount Vernon
• Total:  584 sq mi (1,512.55 km²)
• Land:  571 sq mi (1,478.88 km²)
• Water:  13 sq mi (33.67 km²), 2.2
• Density:  auto/sq mi (/km²)
• Time zone:  Central: UTC-6-5
• Data source:  DuckDuckGo