| | Peekskill, NY | Riverhead, NY | United States |
| Population | 25,304 | 35,630 | 329,725,481 |
| Female Population | 52.6% | 49.5% | 50.5% |
| Male Population | 47.4% | 50.5% | 49.5% |
| Median Age | 40.8 | 49.3 | 38.4 |
| space3 | | | |
| Population - 2010 | 23,605 | 33,538 | 309,327,143 |
| Population - 2000 | 22,441 | 27,680 | 285,036,114 |
| Population - 1990 | 19,536 | 23,011 | 251,960,433 |
| Pop. 2000 to Now | 7.3% | 20.8% | 15.6% |
| Pop. 1990 to Now | 23.3% | 45.3% | 30.8% |
| space4 | | | |
| Population Density | 5,793.0 | 528.4 | 93.4 |
| Land Area | 4.4 | 67.4 | 3,531,905.4 |
| Water Area | 1.2 | 133.8 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Peekskill, NY | Riverhead, NY | United States |
| Age 0 to 4 | 5.4% | 3.9% | 5.9% |
| Age 5 to 9 | 3.6% | 4.8% | 6.1% |
| Age 10 to 14 | 7.4% | 5.2% | 6.6% |
| Age 15 to 17 | 2.9% | 5.6% | 3.9% |
| Age 18 to 20 | 3.1% | 1.8% | 4.0% |
| Age 21 to 24 | 5.6% | 4.2% | 5.2% |
| Age 25 to 34 | 11.7% | 9.2% | 13.8% |
| Age 35 to 44 | 15.5% | 11.0% | 12.9% |
| Age 45 to 54 | 12.7% | 11.2% | 12.6% |
| Age 55 to 59 | 7.9% | 8.0% | 6.7% |
| Age 60 to 64 | 8.9% | 9.6% | 6.3% |
| Age 65 to 74 | 7.6% | 16.3% | 9.6% |
| Age 75 to 84 | 4.8% | 6.8% | 4.5% |
| Age 85 and over | 2.8% | 2.4% | 1.9% |
| space1 | | | |
| Race | | | |
| | Peekskill, NY | Riverhead, NY | United States |
| White | 34.3% | 72.6% | 59.4% |
| Black | 20.4% | 8.5% | 12.2% |
| Asian | 1.9% | 1.9% | 5.6% |
| Native American | 0.1% | 0.1% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.1% | 0.4% | 0.4% |
| Two or More Races | 1.3% | 1.9% | 3.2% |
| Hispanic | 42.0% | 14.6% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Peekskill, NY | Riverhead, NY | United States |
| Married Population | 43.7% | 52.2% | 49.8% |
| Currently Married | 42.3% | 51.1% | 48.0% |
| Married but Separated | 1.4% | 1.1% | 1.8% |
| Single Population | 56.3% | 47.8% | 50.2% |
| Never Married | 37.5% | 29.3% | 33.8% |
| Divorced | 11.9% | 11.9% | 10.8% |
| Widowed | 6.9% | 6.7% | 5.6% |
| space5 | | | |
| Household Size | 2.42 | 2.52 | 2.60 |
| Households | 10,404 | 13,875 | 124,010,992 |
| Family Households | 6,175 | 9,087 | 80,755,759 |
| Married couple, w/children | 31.0% | 29.4% | 30.5% |
| Married couple, no children | 35.5% | 51.1% | 42.9% |
| Non Family Households | 4,229 | 4,788 | 43,255,233 |
| Single householder, w/children | 14.3% | 8.1% | 15.8% |
| Single householder, no children | 19.2% | 11.5% | 10.8% |