Fairfield is the county seat of and the only city in Camas County, Idaho, United States. The population was 416 at the 2010 census, nearly half of the rural county's population. The town was also featured in a season 2 episode of the X-Files, whereupon an investigation at a fictitious zoo took place.
Fairfield is located at 43°20′46″N 114°47′28″W (43.346000, -114.791159), at an elevation of 5,066 feet (1,544 m) above sea level.
According to the United States Census Bureau, the city has a total area of 0.88 square miles (2.28 km2), all of it land.
As of the census of 2020, there were 414 people, 176 households, and 109 families residing in the city. The population density was 472.7 inhabitants per square mile (182.5/km2). There were 244 housing units at an average density of 277.3 per square mile (107.1/km2). The racial makeup of the city was 93.0% White, 1.0% Native American, 0.2% Asian, 1.4% from other races, and 4.3% from two or more races. Hispanic or Latino of any race were 6.3% of the population.
There were 176 households, of which 35.2% had children under the age of 18 living with them, 44.9% were married couples living together, 6.8% had a female householder with no husband present, 10.2% had a male householder with no wife present, and 38.1% were non-families.