| | Hartsville, SC | Fountain Inn, SC | United States |
| Population | 7,565 | 10,237 | 329,725,481 |
| Female Population | 55.0% | 50.8% | 50.5% |
| Male Population | 45.0% | 49.2% | 49.5% |
| Median Age | 29.8 | 32.6 | 38.4 |
| space3 | | | |
| Population - 2010 | 7,732 | 7,659 | 309,327,143 |
| Population - 2000 | 7,556 | 6,017 | 285,036,114 |
| Population - 1990 | 8,372 | 4,388 | 251,960,433 |
| Pop. 2000 to Now | -1.0% | 81.2% | 15.6% |
| Pop. 1990 to Now | -10.7% | 148.5% | 30.8% |
| space4 | | | |
| Population Density | 1,324.6 | 1,409.7 | 93.4 |
| Land Area | 5.7 | 7.3 | 3,531,905.4 |
| Water Area | 0.5 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Hartsville, SC | Fountain Inn, SC | United States |
| Age 0 to 4 | 9.1% | 8.8% | 5.9% |
| Age 5 to 9 | 9.1% | 8.4% | 6.1% |
| Age 10 to 14 | 8.6% | 8.0% | 6.6% |
| Age 15 to 17 | 3.7% | 3.4% | 3.9% |
| Age 18 to 20 | 6.7% | 2.8% | 4.0% |
| Age 21 to 24 | 5.6% | 4.6% | 5.2% |
| Age 25 to 34 | 11.5% | 18.3% | 13.8% |
| Age 35 to 44 | 8.2% | 15.4% | 12.9% |
| Age 45 to 54 | 11.1% | 10.6% | 12.6% |
| Age 55 to 59 | 7.6% | 7.6% | 6.7% |
| Age 60 to 64 | 3.6% | 4.4% | 6.3% |
| Age 65 to 74 | 9.2% | 4.9% | 9.6% |
| Age 75 to 84 | 3.8% | 2.4% | 4.5% |
| Age 85 and over | 2.2% | 0.6% | 1.9% |
| space1 | | | |
| Race | | | |
| | Hartsville, SC | Fountain Inn, SC | United States |
| White | 47.4% | 59.3% | 59.4% |
| Black | 49.5% | 26.3% | 12.2% |
| Asian | 0.8% | 0.1% | 5.6% |
| Native American | 0.0% | 0.2% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.0% | 0.4% |
| Two or More Races | 1.0% | 5.2% | 3.2% |
| Hispanic | 1.4% | 8.9% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Hartsville, SC | Fountain Inn, SC | United States |
| Married Population | 36.5% | 58.8% | 49.8% |
| Currently Married | 32.9% | 57.4% | 48.0% |
| Married but Separated | 3.6% | 1.4% | 1.8% |
| Single Population | 63.5% | 41.2% | 50.2% |
| Never Married | 44.6% | 29.1% | 33.8% |
| Divorced | 12.0% | 8.4% | 10.8% |
| Widowed | 6.9% | 3.7% | 5.6% |
| space5 | | | |
| Household Size | 2.46 | 2.87 | 2.60 |
| Households | 2,859 | 3,547 | 124,010,992 |
| Family Households | 1,647 | 2,838 | 80,755,759 |
| Married couple, w/children | 20.6% | 41.5% | 30.5% |
| Married couple, no children | 33.0% | 32.8% | 42.9% |
| Non Family Households | 1,212 | 709 | 43,255,233 |
| Single householder, w/children | 32.1% | 17.4% | 15.8% |
| Single householder, no children | 14.3% | 8.3% | 10.8% |