[2] Mahaska County comprises the Oskaloosa, IA Micropolitan Statistical Area.

The first school, a small log cabin one-half mile (ca.

The first tracks of the Des Moines Valley Railroad were laid through the county in 1864.

[5] During the 19th century, Muchakinock, about 5 miles (8.0 km) south of Oskaloosa, was probably the largest and most prosperous coal camp in Iowa.

[13] As of the census[14] of 2000, there were 22,335 people, 8,880 households, and 6,144 families residing in the county.

26.60% of all households were made up of individuals, and 12.40% 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 Mahaska County.

Only six Republican Party presidential candidates from 1880 to the present day have failed to win the county, most recently Barry Goldwater in 1964 in his landslide loss statewide & nationally to Lyndon B. Johnson.