| | Seneca, IL | Mauston, WI | United States |
| Population | 2,648 | 4,317 | 329,725,481 |
| Female Population | 51.7% | 41.9% | 50.5% |
| Male Population | 48.3% | 58.1% | 49.5% |
| Median Age | 32.8 | 43.8 | 38.4 |
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| Population - 2010 | 2,352 | 4,418 | 309,327,143 |
| Population - 2000 | 2,053 | 3,740 | 285,036,114 |
| Population - 1990 | 1,878 | 3,439 | 251,960,433 |
| Pop. 2000 to Now | 8.0% | 16.5% | 15.6% |
| Pop. 1990 to Now | 18.1% | 26.7% | 30.8% |
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| Population Density | 402.0 | 965.8 | 93.4 |
| Land Area | 6.6 | 4.5 | 3,531,905.4 |
| Water Area | 0.4 | 0.4 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Seneca, IL | Mauston, WI | United States |
| Age 0 to 4 | 9.4% | 4.8% | 5.9% |
| Age 5 to 9 | 7.1% | 2.7% | 6.1% |
| Age 10 to 14 | 6.9% | 6.7% | 6.6% |
| Age 15 to 17 | 4.4% | 4.4% | 3.9% |
| Age 18 to 20 | 3.0% | 4.1% | 4.0% |
| Age 21 to 24 | 5.2% | 4.4% | 5.2% |
| Age 25 to 34 | 15.8% | 14.8% | 13.8% |
| Age 35 to 44 | 7.4% | 11.5% | 12.9% |
| Age 45 to 54 | 12.8% | 13.8% | 12.6% |
| Age 55 to 59 | 7.3% | 6.9% | 6.7% |
| Age 60 to 64 | 9.8% | 6.3% | 6.3% |
| Age 65 to 74 | 6.6% | 10.4% | 9.6% |
| Age 75 to 84 | 3.0% | 6.6% | 4.5% |
| Age 85 and over | 1.3% | 2.7% | 1.9% |
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| Race | | | |
| | Seneca, IL | Mauston, WI | United States |
| White | 88.0% | 89.1% | 59.4% |
| Black | 1.4% | 5.1% | 12.2% |
| Asian | 0.0% | 1.4% | 5.6% |
| Native American | 0.0% | 0.5% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.0% | 0.4% |
| Two or More Races | 2.6% | 2.0% | 3.2% |
| Hispanic | 8.0% | 1.9% | 18.4% |
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| Marriage & Family | | | |
| | Seneca, IL | Mauston, WI | United States |
| Married Population | 50.8% | 40.8% | 49.8% |
| Currently Married | 47.8% | 39.7% | 48.0% |
| Married but Separated | 3.1% | 1.0% | 1.8% |
| Single Population | 49.2% | 59.2% | 50.2% |
| Never Married | 30.2% | 40.4% | 33.8% |
| Divorced | 15.6% | 12.5% | 10.8% |
| Widowed | 3.4% | 6.3% | 5.6% |
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| Household Size | 2.74 | 2.32 | 2.60 |
| Households | 966 | 1,596 | 124,010,992 |
| Family Households | 752 | 826 | 80,755,759 |
| Married couple, w/children | 23.4% | 33.1% | 30.5% |
| Married couple, no children | 40.3% | 44.4% | 42.9% |
| Non Family Households | 214 | 770 | 43,255,233 |
| Single householder, w/children | 26.1% | 13.3% | 15.8% |
| Single householder, no children | 10.2% | 9.2% | 10.8% |