As of the 2010 United States Census, there were 18,728 people, 5,720 households, and 4,410 families living in the county. The population density was . There were 6,242 housing units at an average density of . The racial makeup of the county was 62.5% white, 1.9% American Indian, 0.7% Asian, 0.6% black or African American, 31.5% from other races, and 2.8% from two or more races. Those of Hispanic or Latino origin made up 59.3% of the population. In terms of ancestry, 16.4% were German, 6.8% were Irish, 5.6% were English, and 2.2% were American.