2000 16,788 1990 16,773 1980 18,229 1970 16,793 1960 17,683 1950 19,723 1940 21,787 1930 23,238 1920 27,625 1910 18,865 1900 15,252 1890 13,154 1880 12,025 1870 10,840 1860 9,422 1850 8,661 1840 8,274 1830 5,692
As of the census of 2000, there were 16,788 people, 6,762 households, and 4,713 families residing in the county. The population density was 65 people per square mile (25/km²). There were 7,405 housing units at an average density of 29 per square mile (11/km²). The racial makeup of the county was 98.39% White, 0.26% Black or African American, 0.24% Native American, 0.12% Asian, 0.02% Pacific Islander, 0.16% from other races, and 0.80% from two or more races. 0.64% of the population were Hispanic or Latino of any race. 22.7% were of American, 16.5% German, 13.2% English, 11.0% Italian and 9.5% Irish ancestry according to Census 2000.
There were 6,762 households out of which 30.80% had children under the age of 18 living with them, 57.30% were married couples living together, 9.00% had a female householder with no husband present, and 30.30% were non-families. 26.60% of all households were made up of individuals and 12.90% had someone living alone who was 65 years of age or older. The average household size was 2.44 and the average family size was 2.94.
In the county the population was spread out with 23.80% under the age of 18, 8.10% from 18 to 24, 27.50% from 25 to 44, 24.90% from 45 to 64, and 15.80% who were 65 years of age or older. The median age was 39 years. For every 100 females there were 95.00 males. For every 100 females age 18 and over, there were 92.00 males.
The median income for a household in the county was $34,837, and the median income for a family was $41,809. Males had a median income of $32,279 versus $22,647 for females. The per capita income for the county was $18,579. About 6.30% of families and 9.50% of the population were below the poverty line, including 10.40% of those under age 18 and 12.60% of those age 65 or over.