| | Stewartville, MN | St. Charles, MN | United States |
| Population | 6,620 | 3,962 | 329,725,481 |
| Female Population | 55.8% | 48.7% | 50.5% |
| Male Population | 44.2% | 51.3% | 49.5% |
| Median Age | 33.4 | 40.8 | 38.4 |
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| Population - 2010 | 5,928 | 3,740 | 309,327,143 |
| Population - 2000 | 5,411 | 3,295 | 285,036,114 |
| Population - 1990 | 4,520 | 2,642 | 251,960,433 |
| Pop. 2000 to Now | 12.6% | 14.4% | 15.6% |
| Pop. 1990 to Now | 34.9% | 42.6% | 30.8% |
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| Population Density | 2,046.4 | 1,070.8 | 93.4 |
| Land Area | 3.2 | 3.7 | 3,531,905.4 |
| Water Area | 0.0 | 0.0 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Stewartville, MN | St. Charles, MN | United States |
| Age 0 to 4 | 9.0% | 8.4% | 5.9% |
| Age 5 to 9 | 9.1% | 5.4% | 6.1% |
| Age 10 to 14 | 8.5% | 6.3% | 6.6% |
| Age 15 to 17 | 3.2% | 2.4% | 3.9% |
| Age 18 to 20 | 5.0% | 1.9% | 4.0% |
| Age 21 to 24 | 3.6% | 3.5% | 5.2% |
| Age 25 to 34 | 13.9% | 14.3% | 13.8% |
| Age 35 to 44 | 13.4% | 16.3% | 12.9% |
| Age 45 to 54 | 11.9% | 11.9% | 12.6% |
| Age 55 to 59 | 5.6% | 9.3% | 6.7% |
| Age 60 to 64 | 4.3% | 5.4% | 6.3% |
| Age 65 to 74 | 6.3% | 8.1% | 9.6% |
| Age 75 to 84 | 3.6% | 4.9% | 4.5% |
| Age 85 and over | 2.6% | 1.8% | 1.9% |
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| Race | | | |
| | Stewartville, MN | St. Charles, MN | United States |
| White | 95.1% | 89.7% | 59.4% |
| Black | 0.0% | 0.0% | 12.2% |
| Asian | 0.6% | 5.6% | 5.6% |
| Native American | 0.1% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.7% | 0.4% |
| Two or More Races | 0.9% | 1.2% | 3.2% |
| Hispanic | 3.3% | 2.9% | 18.4% |
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| Marriage & Family | | | |
| | Stewartville, MN | St. Charles, MN | United States |
| Married Population | 53.6% | 57.2% | 49.8% |
| Currently Married | 52.9% | 57.2% | 48.0% |
| Married but Separated | 0.7% | 0.0% | 1.8% |
| Single Population | 46.4% | 42.8% | 50.2% |
| Never Married | 27.8% | 22.9% | 33.8% |
| Divorced | 12.3% | 14.1% | 10.8% |
| Widowed | 6.3% | 5.8% | 5.6% |
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| Household Size | 2.64 | 2.43 | 2.60 |
| Households | 2,475 | 1,619 | 124,010,992 |
| Family Households | 1,591 | 1,055 | 80,755,759 |
| Married couple, w/children | 44.7% | 33.0% | 30.5% |
| Married couple, no children | 34.3% | 50.7% | 42.9% |
| Non Family Households | 884 | 564 | 43,255,233 |
| Single householder, w/children | 16.0% | 8.2% | 15.8% |
| Single householder, no children | 5.1% | 8.1% | 10.8% |