Thomas County (standard abbreviation: TH) is a county located in the U.S. state of Kansas. As of the 2010 census, the county population was 7,900. Its county seat is Colby.
According to the U.S. Census Bureau, the county has a total area of 1,075 square miles (2,780 km), of which 1,075 square miles (2,780 km) is land and 0.1 square miles (0.26 km) (0.01%) is water.
As of the census of 2000, there were 8,180 people, 3,226 households, and 2,125 families residing in the county. The population density was 8 people per square mile (3/km²). There were 3,562 housing units at an average density of 3 per square mile (1/km²). The racial makeup of the county was 97.14% White, 0.43% Black or African American, 0.33% Native American, 0.27% Asian, 0.02% Pacific Islander, 0.95% from other races, and 0.86% from two or more races. 1.85% of the population were Hispanic or Latino of any race.
There were 3,226 households out of which 32.90% had children under the age of 18 living with them, 56.10% were married couples living together, 6.90% had a female householder with no husband present, and 34.10% were non-families. 28.40% of all households were made up of individuals and 11.70% had someone living alone who was 65 years of age or older. The average household size was 2.45 and the average family size was 3.04.
In the county, the population was spread out with 26.30% under the age of 18, 13.50% from 18 to 24, 24.40% from 25 to 44, 21.20% from 45 to 64, and 14.60% who were 65 years of age or older. The median age was 35 years. For every 100 females there were 94.60 males. For every 100 females age 18 and over, there were 91.50 males.
The median income for a household in the county was $37,034, and the median income for a family was $45,931. Males had a median income of $33,833 versus $21,310 for females. The per capita income for the county was $19,028. About 6.60% of families and 9.70% of the population were below the poverty line, including 5.90% of those under age 18 and 7.50% of those age 65 or over.