[2] Dunn County comprises the Menomonie Micropolitan Statistical Area and is included in the Eau Claire-Menomonie, WI Combined Statistical Area.

[3][4][5] It is named for Charles Dunn, the territory's first chief justice.

As of the census[13] of 2000, there were 39,858 people, 14,337 households, and 9,261 families residing in the county.

The racial makeup of the county was 96.08% White, 0.34% Black or African American, 0.27% Native American, 2.13% Asian, 0.01% Pacific Islander, 0.37% from other races, and 0.80% from two or more races.

24.40% of all households were made up of individuals, and 9.00% had someone living alone who was 65 years of age or older.