The Forest County Potawatomi Community and the Sokaogon Chippewa Community have reservations in Forest County.
As of the census of 2000, there were 10,024 people, 4,043 households, and 2,769 families residing in the county. The population density was 10 people per square mile (4/km²). There were 8,322 housing units at an average density of 8 per square mile (3/km²). The racial makeup of the county was 85.86% White, 11.30% Native American, 1.18% Black or African American, 0.17% Asian, 0.04% Pacific Islander, 0.23% from other races, and 1.22% from two or more races. 1.08% of the population were Hispanic or Latino of any race. 34.3% were of German, 11.4% Polish, 7.4% Irish and 5.4% American ancestry according to Census 2000. 95.5% spoke English, 1.4% Spanish and 1.0% Potawatomi as their first language.
Out of the 4,043 households, 29.20% have children under the age of 18, 54.00% have a married couple living together, 9.80% had a female householder with no husband present, and 31.50% were non-families. 28.20% of all households were made up of individuals living alone, and 13.20%, of individuals of 65 years of age or older living alone. The average household size was 2.39 and the average family size was 2.89.
The age distribution in the county's population is as follows: 25.30% under the age of 18, 7.80% from 18 to 24, 23.90% from 25 to 44, 23.80% from 45 to 64, and 19.30% 65 years of age or older. The median age is 40 years. For every 100 females there were 100.20 males. For every 100 females age 18 and over, there were 99.00 males.