Iowa County is a county located in the U.S. state of Iowa. As of the 2020 census, the population was 16,662. The county seat is Marengo. Iowa County is one of seven counties in the United States to share the same name as the state they are located in. The other six counties are Arkansas County, Hawaii County, Idaho County, New York County, Oklahoma …Iowa County is a county located in the U.S. state of Iowa. As of the 2020 census, the population was 16,662. The county seat is Marengo. Iowa County is one of seven counties in the United States to share the same name as the state they are located in. The other six counties are Arkansas County, Hawaii County, Idaho County, New York County, Oklahoma County, and Utah County.