 According to the 2010–2015 American Community Survey, the largest ancestry groups were German (26.3%), Norwegian (12.6%), Irish (10.8%), and Swedish (8.3%).At the 2000 Census, there were 1,116,200 people, 456,129 households, and 267,291 families living in the county.The population density was 774/km² (2,005/mi²).