| | Rochester, IL | Fountain, CO | United States |
| Population | 3,940 | 29,495 | 329,725,481 |
| Female Population | 52.9% | 50.1% | 50.5% |
| Male Population | 47.1% | 49.9% | 49.5% |
| Median Age | 42.6 | 30.3 | 38.4 |
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| Population - 2010 | 3,725 | 26,106 | 309,327,143 |
| Population - 2000 | 2,893 | 15,197 | 285,036,114 |
| Population - 1990 | 2,676 | 9,984 | 251,960,433 |
| Pop. 2000 to Now | 28.4% | 104.1% | 15.6% |
| Pop. 1990 to Now | 38.8% | 210.7% | 30.8% |
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| Population Density | 1,619.4 | 1,313.6 | 93.4 |
| Land Area | 2.4 | 22.5 | 3,531,905.4 |
| Water Area | 0.0 | 0.0 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Rochester, IL | Fountain, CO | United States |
| Age 0 to 4 | 5.2% | 7.4% | 5.9% |
| Age 5 to 9 | 7.9% | 6.0% | 6.1% |
| Age 10 to 14 | 7.9% | 9.1% | 6.6% |
| Age 15 to 17 | 6.9% | 5.8% | 3.9% |
| Age 18 to 20 | 3.0% | 3.0% | 4.0% |
| Age 21 to 24 | 2.2% | 7.2% | 5.2% |
| Age 25 to 34 | 7.7% | 17.8% | 13.8% |
| Age 35 to 44 | 12.0% | 16.6% | 12.9% |
| Age 45 to 54 | 12.5% | 12.7% | 12.6% |
| Age 55 to 59 | 6.9% | 5.6% | 6.7% |
| Age 60 to 64 | 7.8% | 3.0% | 6.3% |
| Age 65 to 74 | 14.1% | 3.7% | 9.6% |
| Age 75 to 84 | 3.0% | 1.4% | 4.5% |
| Age 85 and over | 2.8% | 0.7% | 1.9% |
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| Race | | | |
| | Rochester, IL | Fountain, CO | United States |
| White | 93.5% | 54.4% | 59.4% |
| Black | 0.3% | 10.4% | 12.2% |
| Asian | 1.8% | 2.7% | 5.6% |
| Native American | 0.0% | 0.4% | 0.6% |
| Hawaiian, Pacific Islander | 0.3% | 0.2% | 0.2% |
| Other | 0.0% | 0.0% | 0.4% |
| Two or More Races | 2.2% | 4.5% | 3.2% |
| Hispanic | 2.0% | 27.3% | 18.4% |
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| Marriage & Family | | | |
| | Rochester, IL | Fountain, CO | United States |
| Married Population | 59.9% | 58.6% | 49.8% |
| Currently Married | 58.6% | 57.5% | 48.0% |
| Married but Separated | 1.3% | 1.1% | 1.8% |
| Single Population | 40.1% | 41.4% | 50.2% |
| Never Married | 23.6% | 28.6% | 33.8% |
| Divorced | 10.6% | 10.4% | 10.8% |
| Widowed | 5.9% | 2.4% | 5.6% |
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| Household Size | 2.70 | 2.94 | 2.60 |
| Households | 1,459 | 10,044 | 124,010,992 |
| Family Households | 1,119 | 7,204 | 80,755,759 |
| Married couple, w/children | 36.7% | 45.7% | 30.5% |
| Married couple, no children | 44.8% | 35.6% | 42.9% |
| Non Family Households | 340 | 2,840 | 43,255,233 |
| Single householder, w/children | 8.0% | 12.9% | 15.8% |
| Single householder, no children | 10.5% | 5.8% | 10.8% |