2000 30,043 1990 24,960 1980 26,138 1970 20,429 1960 18,842 1950 17,031 1940 14,397 1930 13,388 1920 13,961 1910 13,044 1900 14,292 1890 11,185 1880 9,464 1870 6,354 1860 4,291 1850 3,540 1840 1,267
As of the census of 2000, there were 30,043 people, 10,686 households, and 8,217 families residing in the county. The population density was 54 people per square mile (21/km²). There were 11,236 housing units at an average density of 20 per square mile (8/km²). The racial makeup of the county was 97.97% White, 0.35% Black or African American, 0.18% Native American, 0.19% Asian, 0.63% from other races, and 0.68% from two or more races. 2.44% of the population were Hispanic or Latino of any race. 24.9% were of German, 13.2% Dutch, 12.9% American, 10.5% Irish, 8.4% English and 5.9% Polish ancestry according to Census 2000.
There were 10,686 households out of which 36.40% had children under the age of 18 living with them, 65.40% were married couples living together, 7.70% had a female householder with no husband present, and 23.10% were non-families. 19.90% of all households were made up of individuals and 9.30% had someone living alone who was 65 years of age or older. The average household size was 2.72 and the average family size was 3.13.
In the county the population was spread out with 27.40% under the age of 18, 10.10% from 18 to 24, 27.70% from 25 to 44, 22.30% from 45 to 64, and 12.40% who were 65 years of age or older. The median age was 35 years. For every 100 females there were 98.20 males. For every 100 females age 18 and over, there were 95.40 males.
The median income for a household in the county was $43,369, and the median income for a family was $50,132. Males had a median income of $38,544 versus $22,191 for females. The per capita income for the county was $19,012. About 4.60% of families and 6.70% of the population were below the poverty line, including 8.00% of those under age 18 and 5.10% of those age 65 or over.