[2] The county was founded by European-American migrants from eastern areas in 1851.

[3] It was named in honor of Richard Montgomery, an American Revolutionary War general killed in 1775 while trying to capture Quebec City, Canada.

It is famous as the location of the unsolved Villisca axe murders committed in 1912.

90.29% were non-Hispanic White, 0.24% were Black, 3.59% were Hispanic, 0.34% were Native American, 0.25% were Asian, 0.02% were Native Hawaiian or Pacific Islander and 5.27% were some other race or more than one race.

There were 5,399 housing units at an average density of 13 per square mile (5.0/km2).

The racial makeup of the county was 98.20% White, 0.08% Black or African American, 0.35% Native American, 0.25% Asian, 0.01% Pacific Islander, 0.68% from other races, and 0.44% from two or more races.

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