The most important field crops by acres harvested in 2017 were hay and haylage at 48,887 acres, corn (silage) at 37,042 acres, corn (grain) at 22,846 acres, soybeans at 15,000 acres, wheat at 9,975 acres, oats at 2,834 acres, and barley at 146 acres. Both sale prices and rental values of agricultural land are higher than the average for Wisconsin counties. The most common USDA soil association in the county is the Hortonville–Symco association. About 51 percent of soils in this association are Hortonville and 16 percent are Symco. The remaining 33% in the association are minor soils such as Carbondale, Pella, and Kolberg. Altogether, about 34.8% of the county has Hortonville-Symco association soils. In a forested environment, Hortonville and Symco soils have an average of 7.6% and 13.2% organic matter, respectably. However, as cropland they only have tested from 2% to 3% organic matter. According to the U.S. Census Bureau, the county has a total area of , of which is land and (68%) is water. The northern part of the county is on the Door Peninsula between Green Bay and Lake Michigan. The northern part of the Kettle Moraine extends into Kewaunee County. There are three named peaks in the county. The USGS monitors one well in the county on an hourly basis. It also takes hourly pictures of the field in front of the well. It usually takes four to five hours for the groundwater level to rise after a big rain. As of the census of 2000, there were 20,187 people, 7,623 households, and 5,549 families residing in the county. The population density was 59 people per square mile (23/km²). There were 8,221 housing units at an average density of 24 per square mile (9/km²). The racial makeup of the county was 98.56% White, 0.15% Black or African American, 0.27% Native American, 0.13% Asian, 0.30% from other races, and 0.57% from two or more races. 0.76% of the population were Hispanic or Latino of any race. 36.4% were of German, 23.8% Belgian, 9.7% Czech, 6.3% Polish and 5.1% American ancestry. There were 7,623 households out of which 33.50% had children under the age of 18 living with them, 62.40% were married couples living together, 6.60% had a female householder with no husband present, and 27.20% were non-families. 23.50% of all households were made up of individuals and 11.80% had someone living alone who was 65 years of age or older.