| | Gettysburg, PA | Troy, AL | United States |
| Population | 7,423 | 17,765 | 329,725,481 |
| Female Population | 48.8% | 54.4% | 50.5% |
| Male Population | 51.2% | 45.6% | 49.5% |
| Median Age | 24.4 | 25 | 38.4 |
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| Population - 2010 | 7,595 | 18,195 | 309,327,143 |
| Population - 2000 | 7,490 | 13,935 | 285,036,114 |
| Population - 1990 | 7,025 | 13,051 | 251,960,433 |
| Pop. 2000 to Now | 2.9% | 34.6% | 15.6% |
| Pop. 1990 to Now | 9.7% | 43.8% | 30.8% |
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| Population Density | 4,471.7 | 629.6 | 93.4 |
| Land Area | 1.7 | 28.2 | 3,531,905.4 |
| Water Area | 0.0 | 0.1 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Gettysburg, PA | Troy, AL | United States |
| Age 0 to 4 | 2.7% | 4.8% | 5.9% |
| Age 5 to 9 | 2.5% | 6.0% | 6.1% |
| Age 10 to 14 | 3.6% | 3.9% | 6.6% |
| Age 15 to 17 | 3.1% | 2.1% | 3.9% |
| Age 18 to 20 | 29.2% | 15.6% | 4.0% |
| Age 21 to 24 | 9.1% | 17.7% | 5.2% |
| Age 25 to 34 | 12.3% | 11.6% | 13.8% |
| Age 35 to 44 | 9.9% | 10.0% | 12.9% |
| Age 45 to 54 | 8.2% | 7.7% | 12.6% |
| Age 55 to 59 | 3.6% | 4.3% | 6.7% |
| Age 60 to 64 | 4.4% | 5.7% | 6.3% |
| Age 65 to 74 | 6.2% | 5.5% | 9.6% |
| Age 75 to 84 | 4.0% | 3.3% | 4.5% |
| Age 85 and over | 1.1% | 1.8% | 1.9% |
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| Race | | | |
| | Gettysburg, PA | Troy, AL | United States |
| White | 75.3% | 54.0% | 59.4% |
| Black | 3.8% | 38.9% | 12.2% |
| Asian | 2.5% | 3.2% | 5.6% |
| Native American | 0.0% | 0.2% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.0% | 0.4% |
| Two or More Races | 2.9% | 3.1% | 3.2% |
| Hispanic | 15.5% | 0.5% | 18.4% |
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| Marriage & Family | | | |
| | Gettysburg, PA | Troy, AL | United States |
| Married Population | 26.2% | 28.0% | 49.8% |
| Currently Married | 24.9% | 27.4% | 48.0% |
| Married but Separated | 1.2% | 0.6% | 1.8% |
| Single Population | 73.8% | 72.1% | 50.2% |
| Never Married | 59.2% | 58.4% | 33.8% |
| Divorced | 12.1% | 8.9% | 10.8% |
| Widowed | 2.6% | 4.7% | 5.6% |
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| Household Size | 2.08 | 2.54 | 2.60 |
| Households | 2,304 | 6,287 | 124,010,992 |
| Family Households | 1,143 | 2,852 | 80,755,759 |
| Married couple, w/children | 21.2% | 21.1% | 30.5% |
| Married couple, no children | 46.5% | 43.5% | 42.9% |
| Non Family Households | 1,161 | 3,435 | 43,255,233 |
| Single householder, w/children | 12.2% | 25.0% | 15.8% |
| Single householder, no children | 20.0% | 10.4% | 10.8% |