| | Plattsburgh, NY | Sitka, AK | United States |
| Population | 19,969 | 8,518 | 329,725,481 |
| Female Population | 52.6% | 48.3% | 50.5% |
| Male Population | 47.4% | 51.7% | 49.5% |
| Median Age | 29.9 | 39.2 | 38.4 |
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| Population - 2010 | 20,019 | 8,880 | 309,327,143 |
| Population - 2000 | 18,816 | 8,835 | 285,036,114 |
| Population - 1990 | 21,255 | 8,588 | 251,960,433 |
| Pop. 2000 to Now | 2.2% | -4.9% | 15.6% |
| Pop. 1990 to Now | -9.6% | -2.1% | 30.8% |
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| Population Density | 3,962.9 | 3.0 | 93.4 |
| Land Area | 5.0 | 2,870.0 | 3,531,905.4 |
| Water Area | 1.6 | 1,945.1 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Plattsburgh, NY | Sitka, AK | United States |
| Age 0 to 4 | 4.4% | 4.9% | 5.9% |
| Age 5 to 9 | 3.6% | 5.2% | 6.1% |
| Age 10 to 14 | 4.5% | 7.2% | 6.6% |
| Age 15 to 17 | 2.2% | 3.8% | 3.9% |
| Age 18 to 20 | 16.2% | 3.1% | 4.0% |
| Age 21 to 24 | 11.7% | 4.4% | 5.2% |
| Age 25 to 34 | 11.8% | 14.3% | 13.8% |
| Age 35 to 44 | 9.1% | 14.7% | 12.9% |
| Age 45 to 54 | 10.6% | 11.7% | 12.6% |
| Age 55 to 59 | 4.7% | 7.3% | 6.7% |
| Age 60 to 64 | 4.9% | 7.6% | 6.3% |
| Age 65 to 74 | 8.4% | 10.1% | 9.6% |
| Age 75 to 84 | 4.4% | 4.6% | 4.5% |
| Age 85 and over | 3.3% | 1.2% | 1.9% |
| space1 | | | |
| Race | | | |
| | Plattsburgh, NY | Sitka, AK | United States |
| White | 86.8% | 61.4% | 59.4% |
| Black | 3.4% | 0.5% | 12.2% |
| Asian | 2.8% | 7.3% | 5.6% |
| Native American | 0.7% | 9.9% | 0.6% |
| Hawaiian, Pacific Islander | 0.1% | 0.0% | 0.2% |
| Other | 0.0% | 0.3% | 0.4% |
| Two or More Races | 2.1% | 13.4% | 3.2% |
| Hispanic | 4.2% | 7.1% | 18.4% |
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| Marriage & Family | | | |
| | Plattsburgh, NY | Sitka, AK | United States |
| Married Population | 32.2% | 55.0% | 49.8% |
| Currently Married | 29.3% | 53.4% | 48.0% |
| Married but Separated | 2.9% | 1.5% | 1.8% |
| Single Population | 67.8% | 45.0% | 50.2% |
| Never Married | 51.0% | 28.2% | 33.8% |
| Divorced | 10.9% | 12.1% | 10.8% |
| Widowed | 5.9% | 4.7% | 5.6% |
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| Household Size | 1.98 | 2.41 | 2.60 |
| Households | 8,511 | 3,439 | 124,010,992 |
| Family Households | 3,465 | 2,172 | 80,755,759 |
| Married couple, w/children | 22.3% | 30.6% | 30.5% |
| Married couple, no children | 44.5% | 49.8% | 42.9% |
| Non Family Households | 5,046 | 1,267 | 43,255,233 |
| Single householder, w/children | 23.7% | 12.9% | 15.8% |
| Single householder, no children | 9.6% | 6.7% | 10.8% |