| | Northumberland, PA | Dunkirk, NY | United States |
| Population | 3,895 | 12,651 | 329,725,481 |
| Female Population | 50.5% | 49.0% | 50.5% |
| Male Population | 49.5% | 51.0% | 49.5% |
| Median Age | 43 | 42.4 | 38.4 |
| space3 | | | |
| Population - 2010 | 3,776 | 12,527 | 309,327,143 |
| Population - 2000 | 3,714 | 13,131 | 285,036,114 |
| Population - 1990 | 3,860 | 13,989 | 251,960,433 |
| Pop. 2000 to Now | -3.9% | -10.9% | 15.6% |
| Pop. 1990 to Now | -7.5% | -16.4% | 30.8% |
| space4 | | | |
| Population Density | 2,584.6 | 2,808.2 | 93.4 |
| Land Area | 1.5 | 4.5 | 3,531,905.4 |
| Water Area | 0.0 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Northumberland, PA | Dunkirk, NY | United States |
| Age 0 to 4 | 3.0% | 5.3% | 5.9% |
| Age 5 to 9 | 7.3% | 6.0% | 6.1% |
| Age 10 to 14 | 9.3% | 5.0% | 6.6% |
| Age 15 to 17 | 2.6% | 2.7% | 3.9% |
| Age 18 to 20 | 2.7% | 3.3% | 4.0% |
| Age 21 to 24 | 1.4% | 6.0% | 5.2% |
| Age 25 to 34 | 10.3% | 12.8% | 13.8% |
| Age 35 to 44 | 14.9% | 11.7% | 12.9% |
| Age 45 to 54 | 12.2% | 11.9% | 12.6% |
| Age 55 to 59 | 7.8% | 7.6% | 6.7% |
| Age 60 to 64 | 4.7% | 9.7% | 6.3% |
| Age 65 to 74 | 11.0% | 11.6% | 9.6% |
| Age 75 to 84 | 9.2% | 4.7% | 4.5% |
| Age 85 and over | 3.5% | 1.6% | 1.9% |
| space1 | | | |
| Race | | | |
| | Northumberland, PA | Dunkirk, NY | United States |
| White | 90.8% | 61.9% | 59.4% |
| Black | 1.0% | 6.9% | 12.2% |
| Asian | 0.0% | 0.1% | 5.6% |
| Native American | 0.0% | 0.2% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 1.9% | 0.0% | 0.4% |
| Two or More Races | 2.0% | 2.6% | 3.2% |
| Hispanic | 4.3% | 28.2% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Northumberland, PA | Dunkirk, NY | United States |
| Married Population | 57.8% | 37.8% | 49.8% |
| Currently Married | 55.5% | 36.3% | 48.0% |
| Married but Separated | 2.3% | 1.6% | 1.8% |
| Single Population | 42.2% | 62.2% | 50.2% |
| Never Married | 22.5% | 41.5% | 33.8% |
| Divorced | 13.7% | 13.6% | 10.8% |
| Widowed | 6.0% | 7.1% | 5.6% |
| space5 | | | |
| Household Size | 2.25 | 2.11 | 2.60 |
| Households | 1,717 | 5,948 | 124,010,992 |
| Family Households | 1,074 | 3,256 | 80,755,759 |
| Married couple, w/children | 25.4% | 16.3% | 30.5% |
| Married couple, no children | 50.7% | 40.0% | 42.9% |
| Non Family Households | 643 | 2,692 | 43,255,233 |
| Single householder, w/children | 20.7% | 27.2% | 15.8% |
| Single householder, no children | 3.3% | 16.4% | 10.8% |