[2] Established in 1911, the county was named for second U.S. President John Adams.

[4] As of the 2000 United States Census,[11] there were 3,476 people, 1,421 households, and 1,031 families in the county.

23.20% of all households were made up of individuals, and 9.90% had someone living alone who was 65 years of age or older.

As of the 2010 United States Census, there were 3,976 people, 1,748 households, and 1,185 families in the county.

[12] In terms of ancestry, 26.3% were German, 18.0% were English, 14.6% were Irish, and 4.9% were American.

[15] The population ranking of the following table is based on the 2010 census of Adams County.

[26] † county seat School districts include:[28] Residents are in the area (but not the taxation zone) for College of Western Idaho.

[29] The county is served by the Southwest Idaho Health District.