[2] The county was named for General Henry Dodge, governor of Wisconsin Territory.

[14] As of the census[15] of 2000, there were 20,336 people, 7,626 households, and 5,269 families residing in the county.

The racial makeup of the county was 94.78% White, 1.49% Black or African American, 0.24% Native American, 1.88% Asian, 0.02% Pacific Islander, 0.52% from other races, and 1.07% from two or more races.

26.80% of all households were made up of individuals, and 12.20% 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 Henry County.

It has backed Democratic Party candidates in only five elections for president from 1880 to the present.