| | Riverdale, NJ | South Elgin, IL | United States |
| Population | 4,049 | 23,749 | 329,725,481 |
| Female Population | 51.3% | 48.7% | 50.5% |
| Male Population | 48.7% | 51.4% | 49.5% |
| Median Age | 46.1 | 38.6 | 38.4 |
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| Population - 2010 | 3,584 | 22,025 | 309,327,143 |
| Population - 2000 | 2,498 | 16,100 | 285,036,114 |
| Population - 1990 | 2,370 | 7,474 | 251,960,433 |
| Pop. 2000 to Now | 64.7% | 53.1% | 15.6% |
| Pop. 1990 to Now | 73.5% | 229.8% | 30.8% |
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| Population Density | 1,998.5 | 3,362.9 | 93.4 |
| Land Area | 2.0 | 7.1 | 3,531,905.4 |
| Water Area | 0.0 | 0.2 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Riverdale, NJ | South Elgin, IL | United States |
| Age 0 to 4 | 6.1% | 4.0% | 5.9% |
| Age 5 to 9 | 3.2% | 6.8% | 6.1% |
| Age 10 to 14 | 5.2% | 6.6% | 6.6% |
| Age 15 to 17 | 4.7% | 6.1% | 3.9% |
| Age 18 to 20 | 3.5% | 5.5% | 4.0% |
| Age 21 to 24 | 4.1% | 5.0% | 5.2% |
| Age 25 to 34 | 9.9% | 9.5% | 13.8% |
| Age 35 to 44 | 12.0% | 15.5% | 12.9% |
| Age 45 to 54 | 16.3% | 18.9% | 12.6% |
| Age 55 to 59 | 7.9% | 7.2% | 6.7% |
| Age 60 to 64 | 8.0% | 4.3% | 6.3% |
| Age 65 to 74 | 11.3% | 6.2% | 9.6% |
| Age 75 to 84 | 6.0% | 3.0% | 4.5% |
| Age 85 and over | 1.9% | 1.5% | 1.9% |
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| Race | | | |
| | Riverdale, NJ | South Elgin, IL | United States |
| White | 82.2% | 61.9% | 59.4% |
| Black | 1.7% | 5.0% | 12.2% |
| Asian | 2.8% | 8.1% | 5.6% |
| Native American | 0.0% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.4% | 0.4% |
| Two or More Races | 1.4% | 2.5% | 3.2% |
| Hispanic | 12.0% | 22.1% | 18.4% |
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| Marriage & Family | | | |
| | Riverdale, NJ | South Elgin, IL | United States |
| Married Population | 54.0% | 55.3% | 49.8% |
| Currently Married | 50.4% | 54.1% | 48.0% |
| Married but Separated | 3.6% | 1.2% | 1.8% |
| Single Population | 46.0% | 44.7% | 50.2% |
| Never Married | 28.5% | 31.8% | 33.8% |
| Divorced | 12.0% | 9.7% | 10.8% |
| Widowed | 5.6% | 3.2% | 5.6% |
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| Household Size | 2.20 | 2.93 | 2.60 |
| Households | 1,839 | 8,017 | 124,010,992 |
| Family Households | 977 | 6,172 | 80,755,759 |
| Married couple, w/children | 42.1% | 41.5% | 30.5% |
| Married couple, no children | 38.0% | 41.2% | 42.9% |
| Non Family Households | 862 | 1,845 | 43,255,233 |
| Single householder, w/children | 11.1% | 9.5% | 15.8% |
| Single householder, no children | 8.9% | 7.8% | 10.8% |