| | New Castle, NY | Mount Vernon, NY | United States |
| Population | 18,170 | 72,855 | 329,725,481 |
| Female Population | 52.0% | 55.8% | 50.5% |
| Male Population | 48.0% | 44.2% | 49.5% |
| Median Age | 44.4 | 41.6 | 38.4 |
| space3 | | | |
| Population - 2010 | 17,562 | 67,407 | 309,327,143 |
| Population - 2000 | 17,491 | 68,381 | 285,036,114 |
| Population - 1990 | 16,648 | 67,153 | 251,960,433 |
| Pop. 2000 to Now | 0.7% | -2.4% | 15.6% |
| Pop. 1990 to Now | 5.8% | -0.6% | 30.8% |
| space4 | | | |
| Population Density | 781.6 | 16,618.4 | 93.4 |
| Land Area | 23.2 | 4.4 | 3,531,905.4 |
| Water Area | 0.4 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | New Castle, NY | Mount Vernon, NY | United States |
| Age 0 to 4 | 4.7% | 4.5% | 5.9% |
| Age 5 to 9 | 7.0% | 5.5% | 6.1% |
| Age 10 to 14 | 7.9% | 5.6% | 6.6% |
| Age 15 to 17 | 6.2% | 3.3% | 3.9% |
| Age 18 to 20 | 4.1% | 3.3% | 4.0% |
| Age 21 to 24 | 4.4% | 4.1% | 5.2% |
| Age 25 to 34 | 6.6% | 14.8% | 13.8% |
| Age 35 to 44 | 9.9% | 13.2% | 12.9% |
| Age 45 to 54 | 17.2% | 14.5% | 12.6% |
| Age 55 to 59 | 10.3% | 6.9% | 6.7% |
| Age 60 to 64 | 6.7% | 6.6% | 6.3% |
| Age 65 to 74 | 9.3% | 9.7% | 9.6% |
| Age 75 to 84 | 3.0% | 4.6% | 4.5% |
| Age 85 and over | 2.8% | 3.5% | 1.9% |
| space1 | | | |
| Race | | | |
| | New Castle, NY | Mount Vernon, NY | United States |
| White | 81.0% | 17.2% | 59.4% |
| Black | 4.3% | 58.2% | 12.2% |
| Asian | 7.9% | 2.3% | 5.6% |
| Native American | 0.1% | 0.4% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.6% | 1.9% | 0.4% |
| Two or More Races | 2.4% | 2.7% | 3.2% |
| Hispanic | 3.8% | 17.3% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | New Castle, NY | Mount Vernon, NY | United States |
| Married Population | 64.9% | 39.2% | 49.8% |
| Currently Married | 64.3% | 34.9% | 48.0% |
| Married but Separated | 0.6% | 4.3% | 1.8% |
| Single Population | 35.1% | 60.8% | 50.2% |
| Never Married | 27.4% | 42.7% | 33.8% |
| Divorced | 4.6% | 10.7% | 10.8% |
| Widowed | 3.0% | 7.4% | 5.6% |
| space5 | | | |
| Household Size | 3.02 | 2.48 | 2.60 |
| Households | 5,979 | 29,056 | 124,010,992 |
| Family Households | 5,250 | 17,025 | 80,755,759 |
| Married couple, w/children | 42.9% | 21.7% | 30.5% |
| Married couple, no children | 42.7% | 31.4% | 42.9% |
| Non Family Households | 729 | 12,031 | 43,255,233 |
| Single householder, w/children | 6.2% | 21.9% | 15.8% |
| Single householder, no children | 8.2% | 24.9% | 10.8% |