Dubois County is part of the Jasper Micropolitan Statistical Area.
2000 39,674 1990 36,616 1980 34,238 1970 30,934 1960 27,463 1950 23,785 1940 22,579 1930 20,553 1920 19,915 1910 19,843 1900 20,357 1890 20,253 1880 15,992 1870 12,597 1860 10,394 1850 6,321 1840 3,632 1830 1,778 1820 1,168
As of the census of 2000, there were 39,674 people, 14,813 households, and 10,739 families residing in the county. The population density was 92 people per square mile (36/km²). There were 15,511 housing units at an average density of 36 per square mile (14/km²). The racial makeup of the county was 97.54% White, 0.14% Black or African American, 0.10% Native American, 0.20% Asian, 0.04% Pacific Islander, 1.51% from other races, and 0.47% from two or more races. 2.78% of the population were Hispanic or Latino of any race. 64.7% were of German and 15.8% American ancestry according to Census 2000.
There were 14,813 households out of which 37.10% had children under the age of 18 living with them, 61.80% were married couples living together, 7.40% had a female householder with no husband present, and 27.50% were non-families. 23.50% of all households were made up of individuals and 9.90% had someone living alone who was 65 years of age or older. The average household size was 2.63 and the average family size was 3.13.
In the county the population was spread out with 27.40% under the age of 18, 7.90% from 18 to 24, 29.80% from 25 to 44, 22.10% from 45 to 64, and 12.90% who were 65 years of age or older. The median age was 36 years. For every 100 females there were 97.80 males. For every 100 females age 18 and over, there were 96.30 males.
The median income for a household in the county was $44,169, and the median income for a family was $50,342. Males had a median income of $32,484 versus $23,526 for females. The per capita income for the county was $20,225. About 2.90% of families and 6.20% of the population were below the poverty line, including 5.30% of those under age 18 and 7.30% of those age 65 or over.