Monroe is a city in and the county seat of Green County, Wisconsin, United States. The population was 10,661 at the 2020 census. The ci…Monroe is a city in and the county seat of Green County, Wisconsin, United States. The population was 10,661 at the 2020 census. The city is bordered by the town of Monroe to the north and the town of Clarno to the south. Monroe is a part of the Madison metropolitan area. It is nicknamed the "Cheese Capital of the USA".