| | Pocahontas, IL | Centennial, CO | United States |
| Population | 863 | 107,972 | 329,725,481 |
| Female Population | 50.6% | 49.6% | 50.5% |
| Male Population | 49.4% | 50.4% | 49.5% |
| Median Age | 47.1 | 41.4 | 38.4 |
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| Population - 2010 | 790 | 100,294 | 309,327,143 |
| Population - 2000 | 727 | 100,309 | 285,036,114 |
| Population - 1990 | 837 | 81,946 | 251,960,433 |
| Pop. 2000 to Now | -1.0% | 9.8% | 15.6% |
| Pop. 1990 to Now | -14.0% | 34.4% | 30.8% |
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| Population Density | 1,102.2 | 3,650.5 | 93.4 |
| Land Area | 0.8 | 29.6 | 3,531,905.4 |
| Water Area | 0.0 | 0.1 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Pocahontas, IL | Centennial, CO | United States |
| Age 0 to 4 | 5.2% | 5.4% | 5.9% |
| Age 5 to 9 | 6.3% | 6.5% | 6.1% |
| Age 10 to 14 | 5.9% | 7.4% | 6.6% |
| Age 15 to 17 | 3.2% | 4.1% | 3.9% |
| Age 18 to 20 | 1.7% | 2.8% | 4.0% |
| Age 21 to 24 | 2.7% | 3.5% | 5.2% |
| Age 25 to 34 | 14.1% | 11.3% | 13.8% |
| Age 35 to 44 | 10.0% | 14.8% | 12.9% |
| Age 45 to 54 | 7.9% | 13.6% | 12.6% |
| Age 55 to 59 | 12.7% | 7.0% | 6.7% |
| Age 60 to 64 | 10.3% | 7.2% | 6.3% |
| Age 65 to 74 | 15.6% | 10.2% | 9.6% |
| Age 75 to 84 | 3.2% | 4.3% | 4.5% |
| Age 85 and over | 1.0% | 1.9% | 1.9% |
| space1 | | | |
| Race | | | |
| | Pocahontas, IL | Centennial, CO | United States |
| White | 96.4% | 78.0% | 59.4% |
| Black | 0.0% | 2.6% | 12.2% |
| Asian | 0.0% | 5.9% | 5.6% |
| Native American | 0.6% | 0.2% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.2% | 0.2% |
| Other | 0.3% | 0.5% | 0.4% |
| Two or More Races | 1.0% | 3.6% | 3.2% |
| Hispanic | 1.6% | 9.0% | 18.4% |
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| Marriage & Family | | | |
| | Pocahontas, IL | Centennial, CO | United States |
| Married Population | 50.1% | 60.2% | 49.8% |
| Currently Married | 46.0% | 59.4% | 48.0% |
| Married but Separated | 4.1% | 0.7% | 1.8% |
| Single Population | 49.9% | 39.8% | 50.2% |
| Never Married | 33.0% | 25.1% | 33.8% |
| Divorced | 11.5% | 10.9% | 10.8% |
| Widowed | 5.5% | 3.8% | 5.6% |
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| Household Size | 2.77 | 2.63 | 2.60 |
| Households | 311 | 40,344 | 124,010,992 |
| Family Households | 192 | 29,979 | 80,755,759 |
| Married couple, w/children | 32.3% | 36.2% | 30.5% |
| Married couple, no children | 45.3% | 46.3% | 42.9% |
| Non Family Households | 119 | 10,365 | 43,255,233 |
| Single householder, w/children | 10.4% | 10.7% | 15.8% |
| Single householder, no children | 12.0% | 6.8% | 10.8% |