Its county seat is Tazewell.The county is named after William C. C. Claiborne.
There were 11,799 households out of which 32.00% had children under the age of 18 living with them, 58.80% were married couples living together, 11.00% had a female householder with no husband present, and 26.40% were non-families. 23.40% of all households were made up of individuals and 10.00% had someone living alone who was 65 years of age or older. The average household size was 2.48 and the average family size was 2.91.
In the county, the population was spread out with 23.60% under the age of 18, 8.90% from 18 to 24, 28.70% from 25 to 44, 25.40% from 45 to 64, and 13.40% who were 65 years of age or older. The median age was 37 years. For every 100 females there were 93.30 males. For every 100 females age 18 and over, there were 91.40 males.
The median income for a household in the county was $25,782, and the median income for a family was $31,234. Males had a median income of $26,280 versus $19,951 for females. The per capita income for the county was $13,032. About 18.40% of families and 22.60% of the population were below the poverty line, including 27.70% of those under age 18 and 19.90% of those age 65 or over.