| | Ossining, NY | Chappaqua, NY | United States |
| Population | 39,973 | 3,062 | 329,725,481 |
| Female Population | 48.1% | 54.2% | 50.5% |
| Male Population | 51.9% | 45.8% | 49.5% |
| Median Age | 44.2 | 44.3 | 38.4 |
| space3 | | | |
| Population - 2010 | 37,695 | 1,040 | 309,327,143 |
| Population - 2000 | 36,534 | 9,468 | 285,036,114 |
| Population - 1990 | 34,124 | 1,274 | 251,960,433 |
| Pop. 2000 to Now | 2.8% | -86.3% | 15.6% |
| Pop. 1990 to Now | 10.0% | 1.6% | 30.8% |
| space4 | | | |
| Population Density | 3,459.1 | 6,700.2 | 93.4 |
| Land Area | 11.6 | 0.5 | 3,531,905.4 |
| Water Area | 4.2 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Ossining, NY | Chappaqua, NY | United States |
| Age 0 to 4 | 4.5% | 2.6% | 5.9% |
| Age 5 to 9 | 4.5% | 9.5% | 6.1% |
| Age 10 to 14 | 5.9% | 3.4% | 6.6% |
| Age 15 to 17 | 4.5% | 4.8% | 3.9% |
| Age 18 to 20 | 2.8% | 1.9% | 4.0% |
| Age 21 to 24 | 3.7% | 3.8% | 5.2% |
| Age 25 to 34 | 12.3% | 13.4% | 13.8% |
| Age 35 to 44 | 12.7% | 12.5% | 12.9% |
| Age 45 to 54 | 15.9% | 18.6% | 12.6% |
| Age 55 to 59 | 7.7% | 9.2% | 6.7% |
| Age 60 to 64 | 7.0% | 3.2% | 6.3% |
| Age 65 to 74 | 10.4% | 11.5% | 9.6% |
| Age 75 to 84 | 4.5% | 1.0% | 4.5% |
| Age 85 and over | 3.6% | 4.6% | 1.9% |
| space1 | | | |
| Race | | | |
| | Ossining, NY | Chappaqua, NY | United States |
| White | 49.3% | 81.6% | 59.4% |
| Black | 8.2% | 0.0% | 12.2% |
| Asian | 5.4% | 11.2% | 5.6% |
| Native American | 0.0% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.2% | 0.2% |
| Other | 0.7% | 0.9% | 0.4% |
| Two or More Races | 2.9% | 1.9% | 3.2% |
| Hispanic | 33.4% | 4.2% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Ossining, NY | Chappaqua, NY | United States |
| Married Population | 53.8% | 55.8% | 49.8% |
| Currently Married | 51.9% | 55.8% | 48.0% |
| Married but Separated | 1.9% | 0.0% | 1.8% |
| Single Population | 46.2% | 44.2% | 50.2% |
| Never Married | 33.4% | 34.6% | 33.8% |
| Divorced | 9.0% | 7.1% | 10.8% |
| Widowed | 3.7% | 2.5% | 5.6% |
| space5 | | | |
| Household Size | 2.55 | 2.67 | 2.60 |
| Households | 14,628 | 1,143 | 124,010,992 |
| Family Households | 10,310 | 874 | 80,755,759 |
| Married couple, w/children | 32.0% | 35.5% | 30.5% |
| Married couple, no children | 46.6% | 46.6% | 42.9% |
| Non Family Households | 4,318 | 269 | 43,255,233 |
| Single householder, w/children | 9.0% | 8.1% | 15.8% |
| Single householder, no children | 12.4% | 9.8% | 10.8% |