| | West Mifflin, PA | South Park, PA | United States |
| Population | 19,638 | 13,695 | 329,725,481 |
| Female Population | 49.2% | 53.3% | 50.5% |
| Male Population | 50.8% | 46.7% | 49.5% |
| Median Age | 44.2 | 42.9 | 38.4 |
| space3 | | | |
| Population - 2010 | 20,309 | 13,432 | 309,327,143 |
| Population - 2000 | 22,464 | 14,340 | 285,036,114 |
| Population - 1990 | 23,644 | 14,292 | 251,960,433 |
| Pop. 2000 to Now | -12.8% | -5.4% | 15.6% |
| Pop. 1990 to Now | -17.2% | -5.1% | 30.8% |
| space4 | | | |
| Population Density | 1,382.4 | 1,477.4 | 93.4 |
| Land Area | 14.2 | 9.3 | 3,531,905.4 |
| Water Area | 0.3 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | West Mifflin, PA | South Park, PA | United States |
| Age 0 to 4 | 4.9% | 5.1% | 5.9% |
| Age 5 to 9 | 5.2% | 4.7% | 6.1% |
| Age 10 to 14 | 8.0% | 6.3% | 6.6% |
| Age 15 to 17 | 4.0% | 3.5% | 3.9% |
| Age 18 to 20 | 2.7% | 3.6% | 4.0% |
| Age 21 to 24 | 2.7% | 3.1% | 5.2% |
| Age 25 to 34 | 13.6% | 13.0% | 13.8% |
| Age 35 to 44 | 9.5% | 12.9% | 12.9% |
| Age 45 to 54 | 13.1% | 14.6% | 12.6% |
| Age 55 to 59 | 8.4% | 7.2% | 6.7% |
| Age 60 to 64 | 9.7% | 7.6% | 6.3% |
| Age 65 to 74 | 11.2% | 11.8% | 9.6% |
| Age 75 to 84 | 4.9% | 5.4% | 4.5% |
| Age 85 and over | 2.3% | 1.1% | 1.9% |
| space1 | | | |
| Race | | | |
| | West Mifflin, PA | South Park, PA | United States |
| White | 85.3% | 90.4% | 59.4% |
| Black | 9.7% | 2.9% | 12.2% |
| Asian | 0.2% | 3.2% | 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 | 2.9% | 2.5% | 3.2% |
| Hispanic | 1.9% | 1.1% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | West Mifflin, PA | South Park, PA | United States |
| Married Population | 47.5% | 57.1% | 49.8% |
| Currently Married | 46.6% | 56.1% | 48.0% |
| Married but Separated | 1.0% | 1.1% | 1.8% |
| Single Population | 52.5% | 42.9% | 50.2% |
| Never Married | 33.4% | 27.1% | 33.8% |
| Divorced | 10.4% | 9.9% | 10.8% |
| Widowed | 8.6% | 5.9% | 5.6% |
| space5 | | | |
| Household Size | 2.35 | 2.46 | 2.60 |
| Households | 8,307 | 5,535 | 124,010,992 |
| Family Households | 4,940 | 3,883 | 80,755,759 |
| Married couple, w/children | 23.9% | 26.3% | 30.5% |
| Married couple, no children | 49.6% | 51.4% | 42.9% |
| Non Family Households | 3,367 | 1,652 | 43,255,233 |
| Single householder, w/children | 13.4% | 12.9% | 15.8% |
| Single householder, no children | 13.1% | 9.4% | 10.8% |