| | Seabrook, NH | Greensburg, PA | United States |
| Population | 8,443 | 14,982 | 329,725,481 |
| Female Population | 48.7% | 53.5% | 50.5% |
| Male Population | 51.3% | 46.5% | 49.5% |
| Median Age | 50.9 | 38.3 | 38.4 |
| space3 | | | |
| Population - 2010 | 8,677 | 14,885 | 309,327,143 |
| Population - 2000 | 7,934 | 15,889 | 285,036,114 |
| Population - 1990 | 6,503 | 16,318 | 251,960,433 |
| Pop. 2000 to Now | 11.5% | -11.4% | 15.6% |
| Pop. 1990 to Now | 36.0% | -13.7% | 30.8% |
| space4 | | | |
| Population Density | 949.1 | 3,694.7 | 93.4 |
| Land Area | 8.9 | 4.1 | 3,531,905.4 |
| Water Area | 0.8 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Seabrook, NH | Greensburg, PA | United States |
| Age 0 to 4 | 2.3% | 4.8% | 5.9% |
| Age 5 to 9 | 4.4% | 4.1% | 6.1% |
| Age 10 to 14 | 4.6% | 5.2% | 6.6% |
| Age 15 to 17 | 2.1% | 2.2% | 3.9% |
| Age 18 to 20 | 2.9% | 6.5% | 4.0% |
| Age 21 to 24 | 2.3% | 6.8% | 5.2% |
| Age 25 to 34 | 10.8% | 16.0% | 13.8% |
| Age 35 to 44 | 10.2% | 11.1% | 12.9% |
| Age 45 to 54 | 16.7% | 8.7% | 12.6% |
| Age 55 to 59 | 9.1% | 6.2% | 6.7% |
| Age 60 to 64 | 7.6% | 6.3% | 6.3% |
| Age 65 to 74 | 15.9% | 12.7% | 9.6% |
| Age 75 to 84 | 9.9% | 5.0% | 4.5% |
| Age 85 and over | 1.3% | 4.4% | 1.9% |
| space1 | | | |
| Race | | | |
| | Seabrook, NH | Greensburg, PA | United States |
| White | 91.4% | 90.6% | 59.4% |
| Black | 2.0% | 3.5% | 12.2% |
| Asian | 0.5% | 0.6% | 5.6% |
| Native American | 0.0% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.0% | 0.4% |
| Two or More Races | 4.2% | 4.3% | 3.2% |
| Hispanic | 1.9% | 1.0% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Seabrook, NH | Greensburg, PA | United States |
| Married Population | 51.2% | 39.2% | 49.8% |
| Currently Married | 49.8% | 37.2% | 48.0% |
| Married but Separated | 1.4% | 2.0% | 1.8% |
| Single Population | 48.8% | 60.8% | 50.2% |
| Never Married | 25.0% | 43.1% | 33.8% |
| Divorced | 16.7% | 11.1% | 10.8% |
| Widowed | 7.1% | 6.6% | 5.6% |
| space5 | | | |
| Household Size | 2.27 | 2.04 | 2.60 |
| Households | 3,724 | 6,769 | 124,010,992 |
| Family Households | 2,478 | 3,176 | 80,755,759 |
| Married couple, w/children | 19.0% | 24.6% | 30.5% |
| Married couple, no children | 56.3% | 46.8% | 42.9% |
| Non Family Households | 1,246 | 3,593 | 43,255,233 |
| Single householder, w/children | 5.6% | 19.2% | 15.8% |
| Single householder, no children | 19.1% | 9.4% | 10.8% |