As of the 2000 United States Census, there were 51,229 people, 18,670 households, and 12,340 families residing in the county.  The population density was 49 people per square mile (19/km²).  There were 19,746 housing units at an average density of 19 per square mile (7/km²).  The racial makeup of the county was 93.99% Race (United States Census), 0.52% Race (United States Census) or Race (United States Census), 1.44% Race (United States Census), 0.88% Race (United States Census), 0.03% Race (United States Census), 1.67% from Race (United States Census), and 1.47% from two or more races.  3.65% of the population were Race (United States Census) or Race (United States Census) of any race. 40.4% were of norwegian people and 26.8% German people ancestry.. Which groups are between 12000 and 19000 in size?