| | Williamsport, PA | Clarks Summit, PA | United States |
| Population | 27,908 | 5,122 | 329,725,481 |
| Female Population | 49.5% | 53.0% | 50.5% |
| Male Population | 50.5% | 47.1% | 49.5% |
| Median Age | 31 | 44.6 | 38.4 |
| space3 | | | |
| Population - 2010 | 29,392 | 5,160 | 309,327,143 |
| Population - 2000 | 30,706 | 5,126 | 285,036,114 |
| Population - 1990 | 31,933 | 5,433 | 251,960,433 |
| Pop. 2000 to Now | -8.3% | -5.5% | 15.6% |
| Pop. 1990 to Now | -11.8% | -10.9% | 30.8% |
| space4 | | | |
| Population Density | 3,196.4 | 3,231.6 | 93.4 |
| Land Area | 8.7 | 1.6 | 3,531,905.4 |
| Water Area | 0.7 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Williamsport, PA | Clarks Summit, PA | United States |
| Age 0 to 4 | 5.5% | 3.4% | 5.9% |
| Age 5 to 9 | 6.2% | 4.5% | 6.1% |
| Age 10 to 14 | 5.0% | 7.7% | 6.6% |
| Age 15 to 17 | 3.6% | 3.4% | 3.9% |
| Age 18 to 20 | 11.6% | 3.9% | 4.0% |
| Age 21 to 24 | 7.8% | 5.8% | 5.2% |
| Age 25 to 34 | 15.6% | 14.3% | 13.8% |
| Age 35 to 44 | 10.0% | 7.8% | 12.9% |
| Age 45 to 54 | 10.5% | 10.2% | 12.6% |
| Age 55 to 59 | 6.4% | 6.2% | 6.7% |
| Age 60 to 64 | 4.7% | 9.7% | 6.3% |
| Age 65 to 74 | 8.1% | 12.3% | 9.6% |
| Age 75 to 84 | 3.6% | 9.3% | 4.5% |
| Age 85 and over | 1.4% | 1.6% | 1.9% |
| space1 | | | |
| Race | | | |
| | Williamsport, PA | Clarks Summit, PA | United States |
| White | 77.0% | 89.7% | 59.4% |
| Black | 14.3% | 0.0% | 12.2% |
| Asian | 1.4% | 0.3% | 5.6% |
| Native American | 0.3% | 0.1% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.1% | 2.0% | 0.4% |
| Two or More Races | 4.4% | 1.4% | 3.2% |
| Hispanic | 2.4% | 6.6% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Williamsport, PA | Clarks Summit, PA | United States |
| Married Population | 32.9% | 49.5% | 49.8% |
| Currently Married | 29.7% | 46.7% | 48.0% |
| Married but Separated | 3.2% | 2.8% | 1.8% |
| Single Population | 67.1% | 50.5% | 50.2% |
| Never Married | 51.2% | 33.1% | 33.8% |
| Divorced | 11.0% | 8.6% | 10.8% |
| Widowed | 4.9% | 8.8% | 5.6% |
| space5 | | | |
| Household Size | 2.22 | 2.27 | 2.60 |
| Households | 11,017 | 2,259 | 124,010,992 |
| Family Households | 5,822 | 1,252 | 80,755,759 |
| Married couple, w/children | 19.2% | 23.4% | 30.5% |
| Married couple, no children | 37.2% | 54.5% | 42.9% |
| Non Family Households | 5,195 | 1,007 | 43,255,233 |
| Single householder, w/children | 30.6% | 10.7% | 15.8% |
| Single householder, no children | 13.0% | 11.4% | 10.8% |