Monroe County, Illinois

Monroe County
Monroe County Courthouse in Waterloo
Monroe County Courthouse in Waterloo
Flag of Monroe County
Official seal of Monroe County
Official logo of Monroe County
Map of Illinois highlighting Monroe County
Location within the U.S. state of Illinois
Map of the United States highlighting 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
Founded1816
Named forJames Monroe
SeatWaterloo
Largest cityWaterloo
Area
 • Total398 sq mi (1,030 km2)
 • Land385 sq mi (1,000 km2)
 • Water13 sq mi (30 km2)  3.3%
Population
 (2020)
 • Total34,962
 • Estimate 
(2023)
34,957 Decrease
 • Density88/sq mi (34/km2)
Time zoneUTC−6 (Central)
 • Summer (DST)UTC−5 (CDT)
Congressional district12th
Websitemonroecountyil.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".

  1. ^ "State & County QuickFacts". United States Census Bureau.
  2. ^ "Find a County". National Association of Counties. Retrieved June 7, 2011.