Monroe County is a county located in the state of Florida. As of the 2010 census, the population was 73,090. Its county seat is Key West. Monroe County includes the islands of the Florida Keys.Monroe County comprises the Key West, FL Micropolitan Statistical Area.Although 87% of the county's land area is on the mainland, that region is part of the Everglades and is virtually uninhabited. Over 99% of the county's population lives on the Florida Keys.