Monroe County, Illinois

Monroe County
County
Monroe County Courthouse in Waterloo
Flag Seal Logo
Location within the U.S. state of Illinois
Illinois's location within the U.S.
Coordinates: 38°17′N 90°11′W / 38.28°N 90.18°W / 38.28; -90.18
Country	United States
State	Illinois
Founded	1816
Named for	James Monroe
Seat	Waterloo
Largest city	Waterloo
Area
• Total	398 sq mi (1,030 km2)
• Land	385 sq mi (1,000 km2)
• Water	13 sq mi (30 km2)  3.3%
Population  (2020)
• Total	34,962
• Estimate  (2023)	34,957
• Density	88/sq mi (34/km2)
Time zone	UTC−6 (Central)
• Summer (DST)	UTC−5 (CDT)
Congressional district	12th
Website	monroecountyil.gov

Monroe County is a county located in the U.S. state of Illinois. According to the 2020 census, it had a population of 34,962.^[1] Its county seat and largest city is Waterloo.^[2] Monroe County is included in the St. Louis, MO-IL Metropolitan Statistical Area. It is located in the southern portion of Illinois known historically as "Little Egypt".