| | Mosinee, WI | Portage, WI | United States |
| Population | 4,436 | 10,351 | 329,725,481 |
| Female Population | 53.7% | 47.4% | 50.5% |
| Male Population | 46.4% | 52.6% | 49.5% |
| Median Age | 42.3 | 36.4 | 38.4 |
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| Population - 2010 | 4,005 | 10,321 | 309,327,143 |
| Population - 2000 | 4,063 | 9,728 | 285,036,114 |
| Population - 1990 | 3,820 | 8,640 | 251,960,433 |
| Pop. 2000 to Now | 3.3% | 6.7% | 15.6% |
| Pop. 1990 to Now | 9.8% | 20.2% | 30.8% |
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| Population Density | 565.0 | 1,161.5 | 93.4 |
| Land Area | 7.9 | 8.9 | 3,531,905.4 |
| Water Area | 0.9 | 0.8 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Mosinee, WI | Portage, WI | United States |
| Age 0 to 4 | 2.8% | 7.1% | 5.9% |
| Age 5 to 9 | 3.1% | 4.6% | 6.1% |
| Age 10 to 14 | 6.2% | 5.5% | 6.6% |
| Age 15 to 17 | 1.8% | 2.9% | 3.9% |
| Age 18 to 20 | 5.5% | 3.7% | 4.0% |
| Age 21 to 24 | 10.3% | 6.5% | 5.2% |
| Age 25 to 34 | 14.3% | 16.7% | 13.8% |
| Age 35 to 44 | 8.1% | 15.8% | 12.9% |
| Age 45 to 54 | 12.8% | 10.4% | 12.6% |
| Age 55 to 59 | 6.2% | 6.4% | 6.7% |
| Age 60 to 64 | 6.0% | 5.8% | 6.3% |
| Age 65 to 74 | 11.7% | 8.0% | 9.6% |
| Age 75 to 84 | 7.5% | 4.0% | 4.5% |
| Age 85 and over | 3.6% | 2.6% | 1.9% |
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| Race | | | |
| | Mosinee, WI | Portage, WI | United States |
| White | 97.7% | 84.5% | 59.4% |
| Black | 0.0% | 4.9% | 12.2% |
| Asian | 0.8% | 0.7% | 5.6% |
| Native American | 0.0% | 0.3% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.0% | 0.4% |
| Two or More Races | 1.5% | 2.5% | 3.2% |
| Hispanic | 0.0% | 7.1% | 18.4% |
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| Marriage & Family | | | |
| | Mosinee, WI | Portage, WI | United States |
| Married Population | 39.8% | 40.6% | 49.8% |
| Currently Married | 39.5% | 38.6% | 48.0% |
| Married but Separated | 0.3% | 2.0% | 1.8% |
| Single Population | 60.2% | 59.4% | 50.2% |
| Never Married | 38.1% | 36.6% | 33.8% |
| Divorced | 13.1% | 17.2% | 10.8% |
| Widowed | 9.0% | 5.6% | 5.6% |
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| Household Size | 2.08 | 2.27 | 2.60 |
| Households | 2,127 | 4,119 | 124,010,992 |
| Family Households | 999 | 2,322 | 80,755,759 |
| Married couple, w/children | 24.3% | 26.9% | 30.5% |
| Married couple, no children | 51.0% | 39.3% | 42.9% |
| Non Family Households | 1,128 | 1,797 | 43,255,233 |
| Single householder, w/children | 12.0% | 26.8% | 15.8% |
| Single householder, no children | 12.7% | 7.0% | 10.8% |