Fairfield is the county seat of and the only incorporated city in Camas County, Idaho. The population was 410 at the time of 2010 census, n…Fairfield is the county seat of and the only incorporated city in Camas County, Idaho. The population was 410 at the time of 2010 census, nearly half of the rural county's population. According to the United States Census Bureau, the village has a total area of 0.88 square miles, all of it land.