| | Duncansville, PA | Gettysburg, PA | United States |
| Population | 1,137 | 7,423 | 329,725,481 |
| Female Population | 53.7% | 48.8% | 50.5% |
| Male Population | 46.3% | 51.2% | 49.5% |
| Median Age | 45.4 | 24.4 | 38.4 |
| space3 | | | |
| Population - 2010 | 1,232 | 7,595 | 309,327,143 |
| Population - 2000 | 1,238 | 7,490 | 285,036,114 |
| Population - 1990 | 1,309 | 7,025 | 251,960,433 |
| Pop. 2000 to Now | -7.3% | 2.9% | 15.6% |
| Pop. 1990 to Now | -12.3% | 9.7% | 30.8% |
| space4 | | | |
| Population Density | 2,137.2 | 4,471.7 | 93.4 |
| Land Area | 0.5 | 1.7 | 3,531,905.4 |
| Water Area | 0.0 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Duncansville, PA | Gettysburg, PA | United States |
| Age 0 to 4 | 5.0% | 2.7% | 5.9% |
| Age 5 to 9 | 3.5% | 2.5% | 6.1% |
| Age 10 to 14 | 6.7% | 3.6% | 6.6% |
| Age 15 to 17 | 2.5% | 3.1% | 3.9% |
| Age 18 to 20 | 4.0% | 29.2% | 4.0% |
| Age 21 to 24 | 6.4% | 9.1% | 5.2% |
| Age 25 to 34 | 8.5% | 12.3% | 13.8% |
| Age 35 to 44 | 11.8% | 9.9% | 12.9% |
| Age 45 to 54 | 11.3% | 8.2% | 12.6% |
| Age 55 to 59 | 5.0% | 3.6% | 6.7% |
| Age 60 to 64 | 9.4% | 4.4% | 6.3% |
| Age 65 to 74 | 13.3% | 6.2% | 9.6% |
| Age 75 to 84 | 9.3% | 4.0% | 4.5% |
| Age 85 and over | 3.3% | 1.1% | 1.9% |
| space1 | | | |
| Race | | | |
| | Duncansville, PA | Gettysburg, PA | United States |
| White | 93.0% | 75.3% | 59.4% |
| Black | 0.0% | 3.8% | 12.2% |
| Asian | 1.3% | 2.5% | 5.6% |
| Native American | 0.0% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.3% | 0.0% | 0.4% |
| Two or More Races | 2.0% | 2.9% | 3.2% |
| Hispanic | 3.4% | 15.5% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Duncansville, PA | Gettysburg, PA | United States |
| Married Population | 46.3% | 26.2% | 49.8% |
| Currently Married | 43.8% | 24.9% | 48.0% |
| Married but Separated | 2.5% | 1.2% | 1.8% |
| Single Population | 53.7% | 73.8% | 50.2% |
| Never Married | 28.6% | 59.2% | 33.8% |
| Divorced | 17.6% | 12.1% | 10.8% |
| Widowed | 7.5% | 2.6% | 5.6% |
| space5 | | | |
| Household Size | 2.21 | 2.08 | 2.60 |
| Households | 515 | 2,304 | 124,010,992 |
| Family Households | 277 | 1,143 | 80,755,759 |
| Married couple, w/children | 17.0% | 21.2% | 30.5% |
| Married couple, no children | 49.8% | 46.5% | 42.9% |
| Non Family Households | 238 | 1,161 | 43,255,233 |
| Single householder, w/children | 22.7% | 12.2% | 15.8% |
| Single householder, no children | 10.5% | 20.0% | 10.8% |