As of the census of 2000, there were 19,161 people, 7,473 households, and 5,305 families living in the county. The population density was 10 people per square mile. There were 8,633 housing units at an average density of 5 per square mile. The racial makeup of the county was 87.56% White, 0.27% Black or African American, 3.47% Native American, 0.73% Asian, 0.21% Pacific Islander, 5.02% from other races, and 2.75% from two or more races. 7.81% of the population were Hispanics or Latinos of any race. 17.7% were of German, 14.0% United States or American, 11.1% English and 9.6% Irish ancestry. 90.3% spoke English and 7.8% Spanish as their first language. There were 7,473 households out of which 32.30% had children under the age of 18 living with them, 57.70% were married couples living together, 9.10% had a female householder with no husband present, and 29.00% were non-families. 23.80% of all households were made up of individuals and 9.00% had someone living alone who was 65 years of age or older. The average household size was 2.54 and the average family size was 2.99. The age distribution was 27.10% under the age of 18, 6.50% from 18 to 24, 25.70% from 25 to 44, 27.00% from 45 to 64, and 13.80% who were 65 years of age or older. The median age was 40 years. For every 100 females there were 99.50 males. For every 100 females age 18 and over, there were 98.80 males. The median income for a household in the county was $34,267, and the median income for a family was $40,414. Males had a median income of $36,067 versus $21,922 for females. The per capita income for the county was $16,502. About 12.60% of families and 17.00% of the population were below the poverty line, including 22.50% of those under age 18 and 15.10% of those age 65 or over.
2010 census
As of the 2010 United States Census, there were 20,318 people, 8,327 households, and 5,626 families living in the county. The population density was. There were 9,786 housing units at an average density of. The racial makeup of the county was 87.7% white, 2.4% American Indian, 0.6% Asian, 0.2% black or African American, 0.1% Pacific islander, 5.6% from other races, and 3.3% from two or more races. Those of Hispanic or Latino origin made up 10.7% of the population. In terms of ancestry, Of the 8,327 households, 27.6% had children under the age of 18 living with them, 54.5% were married couples living together, 8.5% had a female householder with no husband present, 32.4% were non-families, and 26.4% of all households were made up of individuals. The average household size was 2.42 and the average family size was 2.88. The median age was 45.3 years. The median income for a household in the county was $37,398 and the median income for a family was $46,012. Males had a median income of $43,588 versus $31,114 for females. The per capita income for the county was $21,553. About 13.7% of families and 19.5% of the population were below the poverty line, including 33.9% of those under age 18 and 9.4% of those age 65 or over.
