[2] Boone County comprises the Boone, IA Micropolitan Statistical Area, which is included in the Des Moines-Ames-West Des Moines, IA Combined Statistical Area.

The land that now forms Boone and several other Iowa counties was ceded by the Sac and Fox nation to the United States in a treaty signed on October 11, 1842.

The first building erected in the new settlement was a double log house, to be used as interim county office and courthouse.

The nearby settlement of Montana was incorporated in 1866, when a railway station was built there.

[7] It continued to grow, and it annexed the settlement of Boonesboro (which had also been incorporated in 1866) in 1887, thus becoming the county seat.

26.70% of all households were made up of individuals, and 11.80% 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 Boone County.

From 1984 to 2012, the county was consistently Democratic in presidential elections, but swung hard in 2016 by 20.7 points to back Republican Donald Trump similar to many other counties in Iowa.