[1] The county seat and largest city is American Falls.

It is named for an early hydroelectric power plant (1902) at the American Falls.

The racial makeup of the county was 83.78% White, 0.09% Black or African American, 3.29% Native American, 0.32% Asian, 0.04% Pacific Islander, 11.10% from other races, and 1.38% from two or more races.

There were 2,560 households, out of which 40.90% had children under the age of 18 living with them, 63.40% were married couples living together, 8.80% had a female householder with no husband present, and 23.10% were non-families.

20.30% of all households were made up of individuals, and 8.80% had someone living alone who was 65 years of age or older.

As of the 2010 United States census, there were 7,817 people, 2,641 households, and 2,019 families living in the county.

[15] The racial makeup of the county was 75.1% white, 2.3% American Indian, 0.4% Asian, 0.3% black or African American, 0.1% Pacific islander, 19.5% from other races, and 2.4% from two or more races.