| | Mankato, MN | St. Peter, MN | United States |
| Population | 43,938 | 11,699 | 329,725,481 |
| Female Population | 50.1% | 49.4% | 50.5% |
| Male Population | 49.9% | 50.6% | 49.5% |
| Median Age | 26.8 | 32.6 | 38.4 |
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| Population - 2010 | 39,932 | 11,193 | 309,327,143 |
| Population - 2000 | 32,427 | 9,747 | 285,036,114 |
| Population - 1990 | 31,477 | 9,421 | 251,960,433 |
| Pop. 2000 to Now | 34.0% | 23.5% | 15.6% |
| Pop. 1990 to Now | 38.0% | 27.7% | 30.8% |
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| Population Density | 2,302.6 | 1,917.9 | 93.4 |
| Land Area | 19.1 | 6.1 | 3,531,905.4 |
| Water Area | 0.4 | 0.2 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Mankato, MN | St. Peter, MN | United States |
| Age 0 to 4 | 5.1% | 4.7% | 5.9% |
| Age 5 to 9 | 4.9% | 3.9% | 6.1% |
| Age 10 to 14 | 4.5% | 4.7% | 6.6% |
| Age 15 to 17 | 2.6% | 3.0% | 3.9% |
| Age 18 to 20 | 13.5% | 15.6% | 4.0% |
| Age 21 to 24 | 16.0% | 9.8% | 5.2% |
| Age 25 to 34 | 15.0% | 11.1% | 13.8% |
| Age 35 to 44 | 10.3% | 11.9% | 12.9% |
| Age 45 to 54 | 7.6% | 8.6% | 12.6% |
| Age 55 to 59 | 3.6% | 4.5% | 6.7% |
| Age 60 to 64 | 4.5% | 6.7% | 6.3% |
| Age 65 to 74 | 6.8% | 8.6% | 9.6% |
| Age 75 to 84 | 4.0% | 4.1% | 4.5% |
| Age 85 and over | 1.5% | 2.8% | 1.9% |
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| Race | | | |
| | Mankato, MN | St. Peter, MN | United States |
| White | 83.5% | 81.9% | 59.4% |
| Black | 6.8% | 4.2% | 12.2% |
| Asian | 3.4% | 2.0% | 5.6% |
| Native American | 0.1% | 0.5% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.3% | 0.4% |
| Two or More Races | 1.7% | 3.9% | 3.2% |
| Hispanic | 4.4% | 7.2% | 18.4% |
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| Marriage & Family | | | |
| | Mankato, MN | St. Peter, MN | United States |
| Married Population | 34.1% | 34.3% | 49.8% |
| Currently Married | 33.4% | 34.2% | 48.0% |
| Married but Separated | 0.7% | 0.2% | 1.8% |
| Single Population | 65.9% | 65.7% | 50.2% |
| Never Married | 54.8% | 49.7% | 33.8% |
| Divorced | 7.6% | 10.8% | 10.8% |
| Widowed | 3.4% | 5.1% | 5.6% |
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| Household Size | 2.35 | 2.30 | 2.60 |
| Households | 17,196 | 3,795 | 124,010,992 |
| Family Households | 8,545 | 2,271 | 80,755,759 |
| Married couple, w/children | 28.5% | 24.7% | 30.5% |
| Married couple, no children | 40.7% | 46.3% | 42.9% |
| Non Family Households | 8,651 | 1,524 | 43,255,233 |
| Single householder, w/children | 18.0% | 20.8% | 15.8% |
| Single householder, no children | 12.8% | 8.2% | 10.8% |