| | Upper St. Clair, PA | Sewickley, PA | United States |
| Population | 20,938 | 3,889 | 329,725,481 |
| Female Population | 50.8% | 53.7% | 50.5% |
| Male Population | 49.2% | 46.3% | 49.5% |
| Median Age | 44 | 38.9 | 38.4 |
| space3 | | | |
| Population - 2010 | 19,545 | 3,819 | 309,327,143 |
| Population - 2000 | 20,053 | 3,902 | 285,036,114 |
| Population - 1990 | 19,562 | 4,134 | 251,960,433 |
| Pop. 2000 to Now | -0.8% | -3.4% | 15.6% |
| Pop. 1990 to Now | 1.7% | -8.9% | 30.8% |
| space4 | | | |
| Population Density | 2,132.6 | 3,892.9 | 93.4 |
| Land Area | 9.8 | 1.0 | 3,531,905.4 |
| Water Area | 0.0 | 0.1 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Upper St. Clair, PA | Sewickley, PA | United States |
| Age 0 to 4 | 6.1% | 6.2% | 5.9% |
| Age 5 to 9 | 6.8% | 6.5% | 6.1% |
| Age 10 to 14 | 7.6% | 7.0% | 6.6% |
| Age 15 to 17 | 5.6% | 3.6% | 3.9% |
| Age 18 to 20 | 2.1% | 3.6% | 4.0% |
| Age 21 to 24 | 3.1% | 5.2% | 5.2% |
| Age 25 to 34 | 8.2% | 12.6% | 13.8% |
| Age 35 to 44 | 11.7% | 12.1% | 12.9% |
| Age 45 to 54 | 15.8% | 13.0% | 12.6% |
| Age 55 to 59 | 9.7% | 6.1% | 6.7% |
| Age 60 to 64 | 5.2% | 4.5% | 6.3% |
| Age 65 to 74 | 8.6% | 7.6% | 9.6% |
| Age 75 to 84 | 5.3% | 7.6% | 4.5% |
| Age 85 and over | 4.2% | 4.3% | 1.9% |
| space1 | | | |
| Race | | | |
| | Upper St. Clair, PA | Sewickley, PA | United States |
| White | 89.6% | 80.3% | 59.4% |
| Black | 1.1% | 8.8% | 12.2% |
| Asian | 6.7% | 2.0% | 5.6% |
| Native American | 0.1% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.3% | 0.9% | 0.4% |
| Two or More Races | 1.0% | 6.8% | 3.2% |
| Hispanic | 1.3% | 1.2% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Upper St. Clair, PA | Sewickley, PA | United States |
| Married Population | 66.1% | 59.4% | 49.8% |
| Currently Married | 65.2% | 58.3% | 48.0% |
| Married but Separated | 0.8% | 1.1% | 1.8% |
| Single Population | 33.9% | 40.6% | 50.2% |
| Never Married | 21.8% | 26.3% | 33.8% |
| Divorced | 5.3% | 8.5% | 10.8% |
| Widowed | 6.9% | 5.9% | 5.6% |
| space5 | | | |
| Household Size | 2.75 | 2.28 | 2.60 |
| Households | 7,575 | 1,702 | 124,010,992 |
| Family Households | 6,090 | 1,070 | 80,755,759 |
| Married couple, w/children | 39.6% | 40.2% | 30.5% |
| Married couple, no children | 45.8% | 43.1% | 42.9% |
| Non Family Households | 1,485 | 632 | 43,255,233 |
| Single householder, w/children | 10.1% | 14.5% | 15.8% |
| Single householder, no children | 4.5% | 2.2% | 10.8% |