| | Forty Fort, PA | Fort Mill, SC | United States |
| Population | 4,212 | 24,069 | 329,725,481 |
| Female Population | 48.4% | 51.2% | 50.5% |
| Male Population | 51.6% | 48.8% | 49.5% |
| Median Age | 39.8 | 36.4 | 38.4 |
| space3 | | | |
| Population - 2010 | 4,157 | 11,671 | 309,327,143 |
| Population - 2000 | 4,579 | 7,587 | 285,036,114 |
| Population - 1990 | 5,049 | 4,930 | 251,960,433 |
| Pop. 2000 to Now | -12.1% | 228.6% | 15.6% |
| Pop. 1990 to Now | -20.3% | 405.7% | 30.8% |
| space4 | | | |
| Population Density | 3,207.9 | 1,236.4 | 93.4 |
| Land Area | 1.3 | 19.5 | 3,531,905.4 |
| Water Area | 0.3 | 0.3 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Forty Fort, PA | Fort Mill, SC | United States |
| Age 0 to 4 | 4.8% | 6.1% | 5.9% |
| Age 5 to 9 | 5.2% | 9.1% | 6.1% |
| Age 10 to 14 | 6.7% | 9.6% | 6.6% |
| Age 15 to 17 | 4.3% | 6.3% | 3.9% |
| Age 18 to 20 | 3.1% | 2.9% | 4.0% |
| Age 21 to 24 | 4.7% | 2.6% | 5.2% |
| Age 25 to 34 | 14.4% | 10.6% | 13.8% |
| Age 35 to 44 | 18.4% | 18.1% | 12.9% |
| Age 45 to 54 | 9.7% | 15.7% | 12.6% |
| Age 55 to 59 | 6.3% | 4.3% | 6.7% |
| Age 60 to 64 | 6.5% | 4.9% | 6.3% |
| Age 65 to 74 | 9.4% | 6.6% | 9.6% |
| Age 75 to 84 | 5.8% | 2.7% | 4.5% |
| Age 85 and over | 0.7% | 0.5% | 1.9% |
| space1 | | | |
| Race | | | |
| | Forty Fort, PA | Fort Mill, SC | United States |
| White | 87.1% | 76.7% | 59.4% |
| Black | 1.4% | 11.3% | 12.2% |
| Asian | 0.0% | 2.4% | 5.6% |
| Native American | 0.0% | 0.2% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.1% | 0.4% |
| Two or More Races | 0.0% | 4.1% | 3.2% |
| Hispanic | 11.5% | 5.2% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Forty Fort, PA | Fort Mill, SC | United States |
| Married Population | 53.7% | 59.6% | 49.8% |
| Currently Married | 51.2% | 58.5% | 48.0% |
| Married but Separated | 2.5% | 1.1% | 1.8% |
| Single Population | 46.3% | 40.4% | 50.2% |
| Never Married | 30.8% | 28.4% | 33.8% |
| Divorced | 12.4% | 9.4% | 10.8% |
| Widowed | 3.1% | 2.6% | 5.6% |
| space5 | | | |
| Household Size | 2.54 | 2.94 | 2.60 |
| Households | 1,655 | 8,173 | 124,010,992 |
| Family Households | 1,092 | 6,665 | 80,755,759 |
| Married couple, w/children | 33.2% | 49.1% | 30.5% |
| Married couple, no children | 43.4% | 28.6% | 42.9% |
| Non Family Households | 563 | 1,508 | 43,255,233 |
| Single householder, w/children | 13.7% | 13.1% | 15.8% |
| Single householder, no children | 9.6% | 9.2% | 10.8% |