| | Willmar, MN | Petoskey, MI | United States |
| Population | 20,823 | 5,856 | 329,725,481 |
| Female Population | 51.6% | 52.3% | 50.5% |
| Male Population | 48.4% | 47.7% | 49.5% |
| Median Age | 34.2 | 41.9 | 38.4 |
| space3 | | | |
| Population - 2010 | 19,580 | 5,656 | 309,327,143 |
| Population - 2000 | 18,351 | 6,080 | 285,036,114 |
| Population - 1990 | 17,531 | 6,056 | 251,960,433 |
| Pop. 2000 to Now | 8.4% | -5.8% | 15.6% |
| Pop. 1990 to Now | 13.5% | -5.4% | 30.8% |
| space4 | | | |
| Population Density | 1,490.4 | 1,140.9 | 93.4 |
| Land Area | 14.0 | 5.1 | 3,531,905.4 |
| Water Area | 1.3 | 0.2 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Willmar, MN | Petoskey, MI | United States |
| Age 0 to 4 | 7.8% | 4.8% | 5.9% |
| Age 5 to 9 | 7.5% | 5.1% | 6.1% |
| Age 10 to 14 | 7.6% | 6.6% | 6.6% |
| Age 15 to 17 | 3.4% | 4.2% | 3.9% |
| Age 18 to 20 | 4.8% | 3.6% | 4.0% |
| Age 21 to 24 | 5.6% | 4.4% | 5.2% |
| Age 25 to 34 | 14.4% | 13.4% | 13.8% |
| Age 35 to 44 | 11.5% | 12.3% | 12.9% |
| Age 45 to 54 | 9.9% | 11.4% | 12.6% |
| Age 55 to 59 | 5.7% | 5.3% | 6.7% |
| Age 60 to 64 | 5.6% | 9.1% | 6.3% |
| Age 65 to 74 | 9.2% | 11.6% | 9.6% |
| Age 75 to 84 | 3.4% | 5.4% | 4.5% |
| Age 85 and over | 3.5% | 3.0% | 1.9% |
| space1 | | | |
| Race | | | |
| | Willmar, MN | Petoskey, MI | United States |
| White | 61.6% | 90.1% | 59.4% |
| Black | 11.1% | 0.8% | 12.2% |
| Asian | 1.1% | 0.1% | 5.6% |
| Native American | 0.6% | 1.4% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.2% | 0.0% | 0.4% |
| Two or More Races | 2.1% | 5.1% | 3.2% |
| Hispanic | 23.4% | 2.5% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Willmar, MN | Petoskey, MI | United States |
| Married Population | 47.4% | 45.1% | 49.8% |
| Currently Married | 46.5% | 44.4% | 48.0% |
| Married but Separated | 0.9% | 0.7% | 1.8% |
| Single Population | 52.6% | 54.9% | 50.2% |
| Never Married | 37.0% | 31.0% | 33.8% |
| Divorced | 9.3% | 18.3% | 10.8% |
| Widowed | 6.3% | 5.6% | 5.6% |
| space5 | | | |
| Household Size | 2.56 | 2.10 | 2.60 |
| Households | 7,775 | 2,645 | 124,010,992 |
| Family Households | 4,857 | 1,487 | 80,755,759 |
| Married couple, w/children | 27.9% | 29.7% | 30.5% |
| Married couple, no children | 43.0% | 34.9% | 42.9% |
| Non Family Households | 2,918 | 1,158 | 43,255,233 |
| Single householder, w/children | 20.2% | 23.5% | 15.8% |
| Single householder, no children | 9.0% | 12.0% | 10.8% |