2000 37,629 1990 34,436 1980 35,501 1970 33,930 1960 32,089 1950 29,122 1940 27,231 1930 26,980 1920 28,490 1910 29,296 1900 29,388 1890 28,025 1880 27,316 1870 23,765 1860 20,888 1850 18,084 1840 14,438 1830 7,317
As of the census of 2000, there were 37,629 people, 14,595 households, and 10,245 families residing in the county. The population density was 75 people per square mile (29/km²). There were 15,678 housing units at an average density of 31 per square mile (12/km²). The racial makeup of the county was 96.77% White, 0.77% Black or African American, 0.19% Native American, 0.42% Asian, 0.03% Pacific Islander, 1.10% from other races, and 0.71% from two or more races. 1.62% of the population were Hispanic or Latino of any race. 23.2% were of German, 22.4% American, 12.9% English and 12.7% Irish ancestry according to Census 2000.
There were 14,595 households out of which 33.40% had children under the age of 18 living with them, 57.60% were married couples living together, 8.60% had a female householder with no husband present, and 29.80% were non-families. 25.30% of all households were made up of individuals and 11.00% had someone living alone who was 65 years of age or older. The average household size was 2.50 and the average family size was 2.97.
In the county the population was spread out with 26.00% under the age of 18, 9.00% from 18 to 24, 28.60% from 25 to 44, 22.60% from 45 to 64, and 13.90% who were 65 years of age or older. The median age was 37 years. For every 100 females there were 99.60 males. For every 100 females age 18 and over, there were 97.80 males.
The median income for a household in the county was $41,297, and the median income for a family was $48,779. Males had a median income of $36,612 versus $23,010 for females. The per capita income for the county was $18,938. About 6.10% of families and 8.30% of the population were below the poverty line, including 11.20% of those under age 18 and 7.00% of those age 65 or over.