According to the U.S. Census Bureau, the county has a total area of, of which is land and is water. The southern part of the county, the part bounded on the east and south by Mexico, is known as the Boot Heel.
As of the 2000 census, there were 5,932 people in the county, organized into 2,152 households, and 1,542 families. The population density was 1 person per square mile. There were 2,848 housing units at an average density of 1 per square mile. The racial makeup of the county was 42% White and about 55% of the population was Hispanic. Size of family households: 592 2-persons, 341 3-persons, 316 4-persons, 165 5-persons, 83 6-persons, 48 7-or-more-persons. The average household size was 2.7 and the average family size was 3.29. In non-family households, there were 684 with 314 male householders, 293 female householders, and 77 non-relatives. In group quarters, there were 85. In the county, the population was spread out with 31.70% under the age of 18, 7.80% from 18 to 24, 25.20% from 25 to 44, 21.70% from 45 to 64, and 13.60% who were 65 years of age or older. The median age was 35 years. For every 100 females there were 99.60 males. For every 100 females age 18 and over, there were 97.00 males. The median income for a household in the county was $31,286. The per capita income for the county was $12,431. 27.8% of the population was below the poverty line. Out of the total population, 38.90% of those under the age of 18 and 17.00% of those 65 and older were living below the poverty line. Unemployment rate in April 2010 was 7.6%.
2010 census
As of the 2010 census, there were 4,894 people, 1,936 households, and 1,286 families residing in the county. The population density was. There were 2,393 housing units at an average density of. The racial makeup of the county was 85.3% white, 0.8% American Indian, 0.6% black or African American, 0.5% Asian, 11.0% from other races, and 1.8% from two or more races. Those of Hispanic or Latino origin made up 56.6% of the population. The largest ancestry groups were:
50.3% Mexican
15.2% German
10.0% English
6.0% Irish
4.4% Dutch
3.6% American
2.1% Scottish
2.0% Italian
1.7% Swedish
1.4% Norwegian
1.0% Polish
Of the 1,936 households, 33.4% had children under the age of 18 living with them, 46.4% were married couplesliving together, 14.2% had a female householder with no husband present, 33.6% were non-families, and 29.1% of all households were made up of individuals. The average household size was 2.49 and the average family size was 3.09. The median age was 40.9 years. The median income for a household in the county was $36,733 and the median income for a family was $41,594. Males had a median income of $43,531 versus $23,482 for females. The per capita income for the county was $17,451. About 20.6% of families and 22.6% of the population were below the poverty line, including 32.3% of those under age 18 and 15.0% of those age 65 or over.
