Monroe County Illinois is located south of Downtown St. Louis with the Mississippi River being its western boundary and St. Clair County being its northern. It was formed in 1816 from St. Clair and Randolph counties and today has a total area of 398 square miles. The county seat is located in Waterloo Illinois. In 2010 the US Census put the population of Monroe County at 32,957.
Below is a list of the larger communities that are found in Monroe County. Click on any of the links to find that community's specific government information such as the address to the city hall, phone numbers of the mayor, city clerk, police department and other information.