| | St. Michael, MN | Buffalo, MN | United States |
| Population | 18,148 | 16,121 | 329,725,481 |
| Female Population | 46.8% | 50.8% | 50.5% |
| Male Population | 53.2% | 49.2% | 49.5% |
| Median Age | 34.5 | 38.3 | 38.4 |
| space3 | | | |
| Population - 2010 | 16,425 | 15,511 | 309,327,143 |
| Population - 2000 | 9,099 | 10,097 | 285,036,114 |
| Population - 1990 | 2,506 | 6,856 | 251,960,433 |
| Pop. 2000 to Now | 102.6% | 66.9% | 15.6% |
| Pop. 1990 to Now | 635.7% | 145.8% | 30.8% |
| space4 | | | |
| Population Density | 555.5 | 2,226.4 | 93.4 |
| Land Area | 32.7 | 7.2 | 3,531,905.4 |
| Water Area | 3.7 | 1.9 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | St. Michael, MN | Buffalo, MN | United States |
| Age 0 to 4 | 7.0% | 7.3% | 5.9% |
| Age 5 to 9 | 9.1% | 8.1% | 6.1% |
| Age 10 to 14 | 8.8% | 5.6% | 6.6% |
| Age 15 to 17 | 6.9% | 3.8% | 3.9% |
| Age 18 to 20 | 3.7% | 2.8% | 4.0% |
| Age 21 to 24 | 3.1% | 4.0% | 5.2% |
| Age 25 to 34 | 12.0% | 12.8% | 13.8% |
| Age 35 to 44 | 14.8% | 13.1% | 12.9% |
| Age 45 to 54 | 15.9% | 13.3% | 12.6% |
| Age 55 to 59 | 6.6% | 5.9% | 6.7% |
| Age 60 to 64 | 4.6% | 6.8% | 6.3% |
| Age 65 to 74 | 5.1% | 9.2% | 9.6% |
| Age 75 to 84 | 2.2% | 5.4% | 4.5% |
| Age 85 and over | 0.1% | 2.0% | 1.9% |
| space1 | | | |
| Race | | | |
| | St. Michael, MN | Buffalo, MN | United States |
| White | 89.6% | 95.3% | 59.4% |
| Black | 3.6% | 0.2% | 12.2% |
| Asian | 1.7% | 1.4% | 5.6% |
| Native American | 0.1% | 0.2% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.4% | 0.0% | 0.4% |
| Two or More Races | 2.6% | 2.0% | 3.2% |
| Hispanic | 2.0% | 0.9% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | St. Michael, MN | Buffalo, MN | United States |
| Married Population | 64.7% | 56.2% | 49.8% |
| Currently Married | 64.4% | 55.8% | 48.0% |
| Married but Separated | 0.4% | 0.4% | 1.8% |
| Single Population | 35.3% | 43.8% | 50.2% |
| Never Married | 24.3% | 27.6% | 33.8% |
| Divorced | 8.1% | 13.3% | 10.8% |
| Widowed | 2.9% | 2.9% | 5.6% |
| space5 | | | |
| Household Size | 2.95 | 2.51 | 2.60 |
| Households | 6,153 | 6,252 | 124,010,992 |
| Family Households | 4,913 | 4,239 | 80,755,759 |
| Married couple, w/children | 55.2% | 32.1% | 30.5% |
| Married couple, no children | 35.0% | 48.8% | 42.9% |
| Non Family Households | 1,240 | 2,013 | 43,255,233 |
| Single householder, w/children | 5.5% | 15.0% | 15.8% |
| Single householder, no children | 4.4% | 4.1% | 10.8% |