Waterloo is a city in and the county seat of Black Hawk County, Iowa, United States. As of the 2020 United States Census the population was 67,314, making it the eighth-most populous city in the state.
Grundy County is a county located in the U.S. state of Iowa. At the 2020 census, the population was 12,329. The county seat is Grundy Center. The county is named for Felix Grundy, former U.S. Attorney General.