Ritzville is a city in Adams County, Washington, United States. The population was 1,767 at the 2020 census. It is the county seat of Ada…Ritzville is a city in Adams County, Washington, United States. The population was 1,767 at the 2020 census. It is the county seat of Adams County. The city is part of the Othello, WA Micropolitan Area, which comprises all of Adams County, and is part of the larger Moses Lake-Othello, WA Combined Statistical Area.