[2] The county was formed on February 17, 1843, and named for Wapello, a Meskwaki chief.

[3] Wapello County is included in the Ottumwa, IA Micropolitan Statistical Area.

28.20% of all households were made up of individuals, and 13.40% had someone living alone who was 65 years of age or older.

The population ranking of the following table is based on the 2020 census of Wapello County.

From 1932 to 2012, the county voted Democratic in every election except two, the nationwide Republican landslides of Dwight D. Eisenhower in 1952 and Richard Nixon in 1972.

Also in 2024, Trump became the first candidate from any party to obtain at least 65% of the county's vote since Lyndon B. Johnson in 1964, and the first Republican to do so since Herbert Hoover in 1928.