As of the 2010 United States Census, there were 40,212 people, 16,933 households, and 11,380 families in the county. The population density was . There were 19,583 housing units at an average density of . The racial makeup of the county was 95.9% white, 0.9% American Indian, 0.5% Asian, 0.2% black or African American, 0.1% Pacific islander, 0.6% from other races, and 1.9% from two or more races. Those of Hispanic or Latino origin made up 3.0% of the population. In terms of ancestry, 28.8% were German, 17.4% were English, 15.9% were Irish, 8.3% were American, 5.7% were Italian, and 5.5% were Norwegian.