2000 38,075 1990 35,427 1980 35,596 1970 34,970 1960 33,814 1950 31,400 1940 29,931 1930 29,073 1920 31,671 1910 28,982 1900 28,901 1890 27,644 1880 21,805 1870 19,036 1860 14,867 1850 7,850 1840 1,579
As of the census of 2000, there were 38,075 people, 14,242 households, and 10,282 families residing in the county. The population density was 100 people per square mile (38/km²). There were 15,269 housing units at an average density of 40 per square mile (15/km²). The racial makeup of the county was 98.15% White, 0.18% Black or African American, 0.41% Native American, 0.31% Asian, 0.01% Pacific Islander, 0.26% from other races, and 0.67% from two or more races. 0.95% of the population were Hispanic or Latino of any race. 39.0% were of German, 21.5% American, 8.4% Irish and 8.1% English ancestry according to Census 2000.
There were 14,242 households out of which 34.40% had children under the age of 18 living with them, 59.40% were married couples living together, 9.10% had a female householder with no husband present, and 27.80% were non-families. 23.60% of all households were made up of individuals and 9.70% had someone living alone who was 65 years of age or older. The average household size was 2.57 and the average family size was 3.04.
In the county the population was spread out with 26.10% under the age of 18, 9.90% from 18 to 24, 28.10% from 25 to 44, 21.80% from 45 to 64, and 14.10% who were 65 years of age or older. The median age was 36 years. For every 100 females there were 94.90 males. For every 100 females age 18 and over, there were 91.70 males.
The median income for a household in the county was $41,620, and the median income for a family was $49,031. Males had a median income of $34,894 versus $21,693 for females. The per capita income for the county was $19,480. About 3.70% of families and 5.50% of the population were below the poverty line, including 6.20% of those under age 18 and 5.70% of those age 65 or over.