| | Lancaster, WI | Bartlett, IL | United States |
| Population | 3,930 | 41,126 | 329,725,481 |
| Female Population | 53.3% | 50.0% | 50.5% |
| Male Population | 46.7% | 50.0% | 49.5% |
| Median Age | 33 | 40.8 | 38.4 |
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| Population - 2010 | 3,877 | 41,280 | 309,327,143 |
| Population - 2000 | 4,070 | 36,706 | 285,036,114 |
| Population - 1990 | 4,192 | 19,373 | 251,960,433 |
| Pop. 2000 to Now | -9.1% | 9.8% | 15.6% |
| Pop. 1990 to Now | -11.7% | 108.1% | 30.8% |
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| Population Density | 1,305.2 | 2,619.7 | 93.4 |
| Land Area | 3.0 | 15.7 | 3,531,905.4 |
| Water Area | 0.0 | 0.2 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Lancaster, WI | Bartlett, IL | United States |
| Age 0 to 4 | 7.2% | 5.7% | 5.9% |
| Age 5 to 9 | 6.0% | 5.9% | 6.1% |
| Age 10 to 14 | 5.2% | 7.0% | 6.6% |
| Age 15 to 17 | 3.7% | 4.4% | 3.9% |
| Age 18 to 20 | 10.7% | 2.8% | 4.0% |
| Age 21 to 24 | 5.6% | 5.5% | 5.2% |
| Age 25 to 34 | 14.5% | 10.9% | 13.8% |
| Age 35 to 44 | 11.6% | 13.0% | 12.9% |
| Age 45 to 54 | 8.0% | 15.8% | 12.6% |
| Age 55 to 59 | 6.5% | 7.2% | 6.7% |
| Age 60 to 64 | 4.9% | 7.2% | 6.3% |
| Age 65 to 74 | 6.8% | 9.1% | 9.6% |
| Age 75 to 84 | 7.2% | 3.7% | 4.5% |
| Age 85 and over | 2.2% | 1.9% | 1.9% |
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| Race | | | |
| | Lancaster, WI | Bartlett, IL | United States |
| White | 96.0% | 63.3% | 59.4% |
| Black | 0.7% | 3.3% | 12.2% |
| Asian | 0.8% | 16.9% | 5.6% |
| Native American | 0.0% | 0.1% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.2% | 0.4% |
| Two or More Races | 0.9% | 1.8% | 3.2% |
| Hispanic | 1.6% | 14.4% | 18.4% |
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| Marriage & Family | | | |
| | Lancaster, WI | Bartlett, IL | United States |
| Married Population | 52.7% | 62.2% | 49.8% |
| Currently Married | 52.3% | 61.4% | 48.0% |
| Married but Separated | 0.4% | 0.9% | 1.8% |
| Single Population | 47.4% | 37.8% | 50.2% |
| Never Married | 35.8% | 28.8% | 33.8% |
| Divorced | 6.5% | 4.3% | 10.8% |
| Widowed | 5.0% | 4.7% | 5.6% |
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| Household Size | 2.62 | 2.94 | 2.60 |
| Households | 1,460 | 13,978 | 124,010,992 |
| Family Households | 1,003 | 11,337 | 80,755,759 |
| Married couple, w/children | 35.2% | 36.3% | 30.5% |
| Married couple, no children | 45.1% | 46.5% | 42.9% |
| Non Family Households | 457 | 2,641 | 43,255,233 |
| Single householder, w/children | 11.8% | 9.5% | 15.8% |
| Single householder, no children | 8.0% | 7.7% | 10.8% |