2000 40,930 1990 38,413 1980 40,936 1970 40,456 1960 40,931 1950 38,793 1940 36,908 1930 34,518 1920 38,333 1910 36,368 1900 34,545 1890 31,152 1880 27,611 1870 24,193 1860 16,843 1850 11,021 1840 5,480 1830 1,162
As of the census of 2000, there were 40,930 people, 15,715 households, and 10,921 families residing in the county. The population density was 99 people per square mile (38/km²). There were 16,620 housing units at an average density of 40 per square mile (16/km²). The racial makeup of the county was 93.70% White, 1.29% Black or African American, 0.31% Native American, 0.54% Asian, 0.04% Pacific Islander, 3.23% from other races, and 0.89% from two or more races. 7.10% of the population were Hispanic or Latino of any race. 27.5% were of German, 23.0% American, 9.1% English and 8.2% Irish ancestry according to Census 2000.
There were 15,715 households out of which 31.70% had children under the age of 18 living with them, 55.90% were married couples living together, 9.40% had a female householder with no husband present, and 30.50% were non-families. 25.90% of all households were made up of individuals and 11.80% had someone living alone who was 65 years of age or older. The average household size was 2.53 and the average family size was 3.01.
In the county the population was spread out with 25.90% under the age of 18, 8.70% from 18 to 24, 28.40% from 25 to 44, 22.60% from 45 to 64, and 14.50% who were 65 years of age or older. The median age was 37 years. For every 100 females there were 101.00 males. For every 100 females age 18 and over, there were 96.90 males.
The median income for a household in the county was $39,193, and the median income for a family was $46,506. Males had a median income of $32,362 versus $22,017 for females. The per capita income for the county was $18,892. About 4.70% of families and 7.60% of the population were below the poverty line, including 9.80% of those under age 18 and 5.30% of those age 65 or over.