| | Chelsea, MI | Middleburg, PA | United States |
| Population | 5,447 | 1,474 | 329,725,481 |
| Female Population | 54.3% | 50.9% | 50.5% |
| Male Population | 45.8% | 49.1% | 49.5% |
| Median Age | 48.7 | 35.2 | 38.4 |
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| Population - 2010 | 4,951 | 1,302 | 309,327,143 |
| Population - 2000 | 4,398 | 1,382 | 285,036,114 |
| Population - 1990 | 3,772 | 1,422 | 251,960,433 |
| Pop. 2000 to Now | 22.3% | -8.7% | 15.6% |
| Pop. 1990 to Now | 42.6% | -11.3% | 30.8% |
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| Population Density | 1,506.4 | 1,669.3 | 93.4 |
| Land Area | 3.6 | 0.9 | 3,531,905.4 |
| Water Area | 0.1 | 0.0 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Chelsea, MI | Middleburg, PA | United States |
| Age 0 to 4 | 4.4% | 6.2% | 5.9% |
| Age 5 to 9 | 6.9% | 11.3% | 6.1% |
| Age 10 to 14 | 3.4% | 4.7% | 6.6% |
| Age 15 to 17 | 3.7% | 2.8% | 3.9% |
| Age 18 to 20 | 5.0% | 4.1% | 4.0% |
| Age 21 to 24 | 0.9% | 3.8% | 5.2% |
| Age 25 to 34 | 9.8% | 17.0% | 13.8% |
| Age 35 to 44 | 11.1% | 4.9% | 12.9% |
| Age 45 to 54 | 11.6% | 17.0% | 12.6% |
| Age 55 to 59 | 4.5% | 3.9% | 6.7% |
| Age 60 to 64 | 7.8% | 7.2% | 6.3% |
| Age 65 to 74 | 12.5% | 8.8% | 9.6% |
| Age 75 to 84 | 11.6% | 6.4% | 4.5% |
| Age 85 and over | 6.7% | 2.0% | 1.9% |
| space1 | | | |
| Race | | | |
| | Chelsea, MI | Middleburg, PA | United States |
| White | 95.6% | 94.6% | 59.4% |
| Black | 0.8% | 0.0% | 12.2% |
| Asian | 0.1% | 0.0% | 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 | 1.9% | 3.9% | 3.2% |
| Hispanic | 1.6% | 1.2% | 18.4% |
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| Marriage & Family | | | |
| | Chelsea, MI | Middleburg, PA | United States |
| Married Population | 56.7% | 45.2% | 49.8% |
| Currently Married | 52.8% | 41.6% | 48.0% |
| Married but Separated | 3.9% | 3.6% | 1.8% |
| Single Population | 43.3% | 54.8% | 50.2% |
| Never Married | 18.8% | 30.8% | 33.8% |
| Divorced | 10.3% | 14.5% | 10.8% |
| Widowed | 14.3% | 9.6% | 5.6% |
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| Household Size | 2.07 | 2.42 | 2.60 |
| Households | 2,571 | 602 | 124,010,992 |
| Family Households | 1,348 | 325 | 80,755,759 |
| Married couple, w/children | 35.8% | 28.9% | 30.5% |
| Married couple, no children | 53.3% | 39.7% | 42.9% |
| Non Family Households | 1,223 | 277 | 43,255,233 |
| Single householder, w/children | 7.5% | 16.0% | 15.8% |
| Single householder, no children | 3.4% | 15.4% | 10.8% |