| | Selinsgrove, PA | Quakertown, PA | United States |
| Population | 5,774 | 9,285 | 329,725,481 |
| Female Population | 51.0% | 51.5% | 50.5% |
| Male Population | 49.0% | 48.5% | 49.5% |
| Median Age | 29.3 | 37.2 | 38.4 |
| space3 | | | |
| Population - 2010 | 5,652 | 8,986 | 309,327,143 |
| Population - 2000 | 5,383 | 8,931 | 285,036,114 |
| Population - 1990 | 5,384 | 8,982 | 251,960,433 |
| Pop. 2000 to Now | 9.9% | -2.0% | 15.6% |
| Pop. 1990 to Now | 9.8% | -2.5% | 30.8% |
| space4 | | | |
| Population Density | 3,153.5 | 4,569.4 | 93.4 |
| Land Area | 1.8 | 2.0 | 3,531,905.4 |
| Water Area | 0.1 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Selinsgrove, PA | Quakertown, PA | United States |
| Age 0 to 4 | 2.7% | 5.8% | 5.9% |
| Age 5 to 9 | 3.0% | 7.4% | 6.1% |
| Age 10 to 14 | 1.6% | 4.2% | 6.6% |
| Age 15 to 17 | 1.8% | 3.5% | 3.9% |
| Age 18 to 20 | 26.6% | 3.6% | 4.0% |
| Age 21 to 24 | 10.7% | 6.6% | 5.2% |
| Age 25 to 34 | 8.5% | 15.5% | 13.8% |
| Age 35 to 44 | 8.5% | 16.7% | 12.9% |
| Age 45 to 54 | 6.6% | 11.4% | 12.6% |
| Age 55 to 59 | 5.1% | 4.5% | 6.7% |
| Age 60 to 64 | 5.3% | 5.8% | 6.3% |
| Age 65 to 74 | 10.1% | 8.8% | 9.6% |
| Age 75 to 84 | 4.7% | 4.2% | 4.5% |
| Age 85 and over | 4.9% | 2.0% | 1.9% |
| space1 | | | |
| Race | | | |
| | Selinsgrove, PA | Quakertown, PA | United States |
| White | 85.4% | 75.9% | 59.4% |
| Black | 4.8% | 3.8% | 12.2% |
| Asian | 1.3% | 2.2% | 5.6% |
| Native American | 0.1% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.1% | 0.4% |
| Two or More Races | 3.2% | 2.9% | 3.2% |
| Hispanic | 5.2% | 15.1% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Selinsgrove, PA | Quakertown, PA | United States |
| Married Population | 31.1% | 39.8% | 49.8% |
| Currently Married | 29.1% | 37.7% | 48.0% |
| Married but Separated | 2.0% | 2.1% | 1.8% |
| Single Population | 68.9% | 60.2% | 50.2% |
| Never Married | 50.7% | 43.4% | 33.8% |
| Divorced | 9.3% | 11.7% | 10.8% |
| Widowed | 8.9% | 5.1% | 5.6% |
| space5 | | | |
| Household Size | 1.87 | 2.58 | 2.60 |
| Households | 1,927 | 3,500 | 124,010,992 |
| Family Households | 884 | 2,116 | 80,755,759 |
| Married couple, w/children | 21.6% | 28.4% | 30.5% |
| Married couple, no children | 55.9% | 36.9% | 42.9% |
| Non Family Households | 1,043 | 1,384 | 43,255,233 |
| Single householder, w/children | 10.0% | 24.0% | 15.8% |
| Single householder, no children | 12.6% | 10.7% | 10.8% |