Thomson is located at (33.467346, -82.499450).
According to the United States Census Bureau, the city has a total area of 3.95 square miles (10.2 km²)
There were 2,609 households out of which 36.2% had children under the age of 18 living with them, 35.7% were married couples living together, 28.4% had a female householder with no husband present, and 31.3% were non-families. 28.2% of all households were made up of individuals and 12.6% had someone living alone who was 65 years of age or older. The average household size was 2.50 and the average family size was 3.05.
In the city the population was spread out with 28.6% under the age of 18, 9.3% from 18 to 24, 27.2% from 25 to 44, 19.6% from 45 to 64, and 15.3% who were 65 years of age or older. The median age was 34 years. For every 100 females there were 81.3 males. For every 100 females age 18 and over, there were 73.5 males.
The median income for a household in the city was $23,179, and the median income for a family was $30,015. Males had a median income of $25,882 versus $20,607 for females. The per capita income for the city was $14,976. 27.6% of the population and 23.8% of families were below the poverty line. 1.7% of those under the age of 18 and 100% of those 65 and older were living below the poverty line.