| | Williamsport, PA | San Francisco, CA | United States |
| Population | 27,908 | 865,933 | 329,725,481 |
| Female Population | 49.5% | 48.8% | 50.5% |
| Male Population | 50.5% | 51.2% | 49.5% |
| Median Age | 31 | 38.7 | 38.4 |
| space3 | | | |
| Population - 2010 | 29,392 | 805,519 | 309,327,143 |
| Population - 2000 | 30,706 | 776,733 | 285,036,114 |
| Population - 1990 | 31,933 | 723,959 | 251,960,433 |
| Pop. 2000 to Now | -8.3% | 11.6% | 15.6% |
| Pop. 1990 to Now | -11.8% | 19.7% | 30.8% |
| space4 | | | |
| Population Density | 3,196.4 | 18,478.0 | 93.4 |
| Land Area | 8.7 | 46.9 | 3,531,905.4 |
| Water Area | 0.7 | 185.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Williamsport, PA | San Francisco, CA | United States |
| Age 0 to 4 | 5.5% | 4.4% | 5.9% |
| Age 5 to 9 | 6.2% | 3.5% | 6.1% |
| Age 10 to 14 | 5.0% | 3.7% | 6.6% |
| Age 15 to 17 | 3.6% | 2.0% | 3.9% |
| Age 18 to 20 | 11.6% | 2.3% | 4.0% |
| Age 21 to 24 | 7.8% | 4.5% | 5.2% |
| Age 25 to 34 | 15.6% | 22.6% | 13.8% |
| Age 35 to 44 | 10.0% | 16.1% | 12.9% |
| Age 45 to 54 | 10.5% | 13.2% | 12.6% |
| Age 55 to 59 | 6.4% | 6.0% | 6.7% |
| Age 60 to 64 | 4.7% | 5.7% | 6.3% |
| Age 65 to 74 | 8.1% | 9.1% | 9.6% |
| Age 75 to 84 | 3.6% | 4.3% | 4.5% |
| Age 85 and over | 1.4% | 2.5% | 1.9% |
| space1 | | | |
| Race | | | |
| | Williamsport, PA | San Francisco, CA | United States |
| White | 77.0% | 39.2% | 59.4% |
| Black | 14.3% | 4.9% | 12.2% |
| Asian | 1.4% | 34.1% | 5.6% |
| Native American | 0.3% | 0.2% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.3% | 0.2% |
| Other | 0.1% | 0.6% | 0.4% |
| Two or More Races | 4.4% | 5.3% | 3.2% |
| Hispanic | 2.4% | 15.4% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Williamsport, PA | San Francisco, CA | United States |
| Married Population | 32.9% | 41.5% | 49.8% |
| Currently Married | 29.7% | 40.1% | 48.0% |
| Married but Separated | 3.2% | 1.4% | 1.8% |
| Single Population | 67.1% | 58.5% | 50.2% |
| Never Married | 51.2% | 46.0% | 33.8% |
| Divorced | 11.0% | 8.0% | 10.8% |
| Widowed | 4.9% | 4.5% | 5.6% |
| space5 | | | |
| Household Size | 2.22 | 2.34 | 2.60 |
| Households | 11,017 | 361,222 | 124,010,992 |
| Family Households | 5,822 | 170,465 | 80,755,759 |
| Married couple, w/children | 19.2% | 28.8% | 30.5% |
| Married couple, no children | 37.2% | 47.0% | 42.9% |
| Non Family Households | 5,195 | 190,757 | 43,255,233 |
| Single householder, w/children | 30.6% | 10.0% | 15.8% |
| Single householder, no children | 13.0% | 14.2% | 10.8% |