According to the U.S. Census Bureau, the county has a total area of 1,506 km² (581 mi²). 1,461 km² (564 mi²) of it is land and 45 km² (17 mi²) of it is water. The total area is 2.99% water.
As of the census2 of 2000, there are 15,757 people, 5,708 households, and 4,223 families residing in the county. The population density is 11/km² (28/mi²). There are 6,434 housing units at an average density of 4/km² (11/mi²). The racial makeup of the county is 79.61% White, 4.94% Black or African American, 1.82% Native American, 0.13% Asian, 0.06% Pacific Islander, 11.84% from other races, and 1.61% from two or more races. 19.72% of the population are Hispanic or Latino of any race.
There are 5,708 households out of which 36.40% have children under the age of 18 living with them, 59.30% are married couples living together, 10.00% have a female householder with no husband present, and 26.00% are non-families. 22.80% of all households are made up of individuals and 11.00% have someone living alone who is 65 years of age or older. The average household size is 2.73 and the average family size is 3.19.
In the county the population is spread out with 28.20% under the age of 18, 9.50% from 18 to 24, 27.70% from 25 to 44, 21.30% from 45 to 64, and 13.20% who are 65 years of age or older. The median age is 34 years. For every 100 females there are 99.10 males. For every 100 females age 18 and over, there are 97.00 males.
The median income for a household in the county is $30,144, and the median income for a family is $34,560. Males have a median income of $25,709 versus $17,666 for females. The per capita income for the county is $14,122. 19.20% of the population and 14.40% of families are below the poverty line. Out of the total people living in poverty, 26.90% are under the age of 18 and 14.20% are 65 or older.