| | Mellen, WI | Sparta, WI | United States |
| Population | 592 | 9,955 | 329,725,481 |
| Female Population | 53.4% | 50.1% | 50.5% |
| Male Population | 46.6% | 49.9% | 49.5% |
| Median Age | 52.6 | 39.4 | 38.4 |
| space3 | | | |
| Population - 2010 | 723 | 9,539 | 309,327,143 |
| Population - 2000 | 845 | 8,648 | 285,036,114 |
| Population - 1990 | 935 | 7,788 | 251,960,433 |
| Pop. 2000 to Now | -18.8% | 13.3% | 15.6% |
| Pop. 1990 to Now | -26.6% | 25.8% | 30.8% |
| space4 | | | |
| Population Density | 317.8 | 1,254.1 | 93.4 |
| Land Area | 1.9 | 7.9 | 3,531,905.4 |
| Water Area | 0.0 | 0.1 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Mellen, WI | Sparta, WI | United States |
| Age 0 to 4 | 4.4% | 5.3% | 5.9% |
| Age 5 to 9 | 2.2% | 6.6% | 6.1% |
| Age 10 to 14 | 6.9% | 7.3% | 6.6% |
| Age 15 to 17 | 2.9% | 5.3% | 3.9% |
| Age 18 to 20 | 7.4% | 2.4% | 4.0% |
| Age 21 to 24 | 3.7% | 3.6% | 5.2% |
| Age 25 to 34 | 5.2% | 14.3% | 13.8% |
| Age 35 to 44 | 9.3% | 12.6% | 12.9% |
| Age 45 to 54 | 10.6% | 12.9% | 12.6% |
| Age 55 to 59 | 9.5% | 8.0% | 6.7% |
| Age 60 to 64 | 15.0% | 6.5% | 6.3% |
| Age 65 to 74 | 12.7% | 10.0% | 9.6% |
| Age 75 to 84 | 7.1% | 3.8% | 4.5% |
| Age 85 and over | 3.0% | 1.5% | 1.9% |
| space1 | | | |
| Race | | | |
| | Mellen, WI | Sparta, WI | United States |
| White | 91.0% | 87.5% | 59.4% |
| Black | 0.0% | 2.0% | 12.2% |
| Asian | 1.0% | 1.2% | 5.6% |
| Native American | 1.2% | 1.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.1% | 0.4% |
| Two or More Races | 1.0% | 2.7% | 3.2% |
| Hispanic | 5.7% | 5.4% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Mellen, WI | Sparta, WI | United States |
| Married Population | 44.7% | 45.4% | 49.8% |
| Currently Married | 44.7% | 42.5% | 48.0% |
| Married but Separated | 0.0% | 2.9% | 1.8% |
| Single Population | 55.3% | 54.6% | 50.2% |
| Never Married | 27.5% | 33.2% | 33.8% |
| Divorced | 15.6% | 16.4% | 10.8% |
| Widowed | 12.1% | 5.0% | 5.6% |
| space5 | | | |
| Household Size | 2.08 | 2.38 | 2.60 |
| Households | 273 | 4,084 | 124,010,992 |
| Family Households | 147 | 2,460 | 80,755,759 |
| Married couple, w/children | 17.0% | 25.2% | 30.5% |
| Married couple, no children | 54.4% | 39.9% | 42.9% |
| Non Family Households | 126 | 1,624 | 43,255,233 |
| Single householder, w/children | 15.6% | 22.9% | 15.8% |
| Single householder, no children | 12.9% | 12.0% | 10.8% |