| | Stewart, MN | Buffalo, MN | United States |
| Population | 609 | 16,121 | 329,725,481 |
| Female Population | 43.7% | 50.8% | 50.5% |
| Male Population | 56.3% | 49.2% | 49.5% |
| Median Age | 33.9 | 38.3 | 38.4 |
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| Population - 2010 | 570 | 15,511 | 309,327,143 |
| Population - 2000 | 564 | 10,097 | 285,036,114 |
| Population - 1990 | 566 | 6,856 | 251,960,433 |
| Pop. 2000 to Now | -5.5% | 66.9% | 15.6% |
| Pop. 1990 to Now | -5.8% | 145.8% | 30.8% |
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| Population Density | 752.8 | 2,226.4 | 93.4 |
| Land Area | 0.8 | 7.2 | 3,531,905.4 |
| Water Area | 0.0 | 1.9 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Stewart, MN | Buffalo, MN | United States |
| Age 0 to 4 | 7.6% | 7.3% | 5.9% |
| Age 5 to 9 | 9.0% | 8.1% | 6.1% |
| Age 10 to 14 | 11.2% | 5.6% | 6.6% |
| Age 15 to 17 | 4.4% | 3.8% | 3.9% |
| Age 18 to 20 | 1.3% | 2.8% | 4.0% |
| Age 21 to 24 | 3.9% | 4.0% | 5.2% |
| Age 25 to 34 | 13.0% | 12.8% | 13.8% |
| Age 35 to 44 | 13.5% | 13.1% | 12.9% |
| Age 45 to 54 | 14.0% | 13.3% | 12.6% |
| Age 55 to 59 | 5.3% | 5.9% | 6.7% |
| Age 60 to 64 | 6.7% | 6.8% | 6.3% |
| Age 65 to 74 | 4.6% | 9.2% | 9.6% |
| Age 75 to 84 | 3.0% | 5.4% | 4.5% |
| Age 85 and over | 2.6% | 2.0% | 1.9% |
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| Race | | | |
| | Stewart, MN | Buffalo, MN | United States |
| White | 79.6% | 95.3% | 59.4% |
| Black | 0.0% | 0.2% | 12.2% |
| Asian | 0.0% | 1.4% | 5.6% |
| Native American | 0.0% | 0.2% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.0% | 0.4% |
| Two or More Races | 0.0% | 2.0% | 3.2% |
| Hispanic | 20.4% | 0.9% | 18.4% |
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| Marriage & Family | | | |
| | Stewart, MN | Buffalo, MN | United States |
| Married Population | 45.5% | 56.2% | 49.8% |
| Currently Married | 45.0% | 55.8% | 48.0% |
| Married but Separated | 0.5% | 0.4% | 1.8% |
| Single Population | 54.5% | 43.8% | 50.2% |
| Never Married | 30.5% | 27.6% | 33.8% |
| Divorced | 21.1% | 13.3% | 10.8% |
| Widowed | 3.0% | 2.9% | 5.6% |
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| Household Size | 2.73 | 2.51 | 2.60 |
| Households | 223 | 6,252 | 124,010,992 |
| Family Households | 114 | 4,239 | 80,755,759 |
| Married couple, w/children | 31.6% | 32.1% | 30.5% |
| Married couple, no children | 44.7% | 48.8% | 42.9% |
| Non Family Households | 109 | 2,013 | 43,255,233 |
| Single householder, w/children | 12.3% | 15.0% | 15.8% |
| Single householder, no children | 11.4% | 4.1% | 10.8% |