| | Clarksville, VA | Altavista, VA | United States |
| Population | 1,542 | 3,396 | 329,725,481 |
| Female Population | 57.1% | 52.9% | 50.5% |
| Male Population | 42.9% | 47.1% | 49.5% |
| Median Age | 48.2 | 41.8 | 38.4 |
| space3 | | | |
| Population - 2010 | 1,232 | 3,456 | 309,327,143 |
| Population - 2000 | 1,329 | 3,425 | 285,036,114 |
| Population - 1990 | 1,243 | 3,686 | 251,960,433 |
| Pop. 2000 to Now | -12.0% | -0.1% | 15.6% |
| Pop. 1990 to Now | -6.0% | -7.2% | 30.8% |
| space4 | | | |
| Population Density | 529.7 | 673.0 | 93.4 |
| Land Area | 2.9 | 5.0 | 3,531,905.4 |
| Water Area | 0.0 | 0.1 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Clarksville, VA | Altavista, VA | United States |
| Age 0 to 4 | 7.1% | 8.1% | 5.9% |
| Age 5 to 9 | 7.5% | 5.4% | 6.1% |
| Age 10 to 14 | 11.0% | 3.9% | 6.6% |
| Age 15 to 17 | 2.0% | 4.6% | 3.9% |
| Age 18 to 20 | 1.0% | 5.5% | 4.0% |
| Age 21 to 24 | 2.6% | 1.2% | 5.2% |
| Age 25 to 34 | 6.2% | 13.1% | 13.8% |
| Age 35 to 44 | 9.0% | 11.9% | 12.9% |
| Age 45 to 54 | 12.9% | 14.2% | 12.6% |
| Age 55 to 59 | 5.4% | 6.9% | 6.7% |
| Age 60 to 64 | 3.3% | 4.4% | 6.3% |
| Age 65 to 74 | 18.8% | 11.7% | 9.6% |
| Age 75 to 84 | 9.8% | 4.7% | 4.5% |
| Age 85 and over | 3.4% | 4.4% | 1.9% |
| space1 | | | |
| Race | | | |
| | Clarksville, VA | Altavista, VA | United States |
| White | 80.5% | 62.4% | 59.4% |
| Black | 15.5% | 36.8% | 12.2% |
| Asian | 0.6% | 0.3% | 5.6% |
| Native American | 0.0% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.0% | 0.4% |
| Two or More Races | 1.5% | 0.5% | 3.2% |
| Hispanic | 1.8% | 0.0% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Clarksville, VA | Altavista, VA | United States |
| Married Population | 47.9% | 40.3% | 49.8% |
| Currently Married | 44.4% | 37.6% | 48.0% |
| Married but Separated | 3.5% | 2.7% | 1.8% |
| Single Population | 52.1% | 59.7% | 50.2% |
| Never Married | 24.4% | 34.6% | 33.8% |
| Divorced | 15.9% | 15.3% | 10.8% |
| Widowed | 11.8% | 9.8% | 5.6% |
| space5 | | | |
| Household Size | 2.19 | 2.48 | 2.60 |
| Households | 704 | 1,338 | 124,010,992 |
| Family Households | 319 | 839 | 80,755,759 |
| Married couple, w/children | 29.8% | 23.7% | 30.5% |
| Married couple, no children | 48.0% | 29.8% | 42.9% |
| Non Family Households | 385 | 499 | 43,255,233 |
| Single householder, w/children | 12.2% | 26.7% | 15.8% |
| Single householder, no children | 10.0% | 19.8% | 10.8% |