| | Lemont, IL | Riverside, CA | United States |
| Population | 17,535 | 314,858 | 329,725,481 |
| Female Population | 49.3% | 50.0% | 50.5% |
| Male Population | 50.7% | 50.0% | 49.5% |
| Median Age | 44 | 31.9 | 38.4 |
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| Population - 2010 | 16,075 | 305,417 | 309,327,143 |
| Population - 2000 | 13,098 | 255,166 | 285,036,114 |
| Population - 1990 | 7,348 | 226,505 | 251,960,433 |
| Pop. 2000 to Now | 32.4% | 29.6% | 15.6% |
| Pop. 1990 to Now | 136.0% | 46.0% | 30.8% |
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| Population Density | 2,167.5 | 3,875.0 | 93.4 |
| Land Area | 8.1 | 81.3 | 3,531,905.4 |
| Water Area | 0.4 | 0.3 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Lemont, IL | Riverside, CA | United States |
| Age 0 to 4 | 4.0% | 6.0% | 5.9% |
| Age 5 to 9 | 8.6% | 6.2% | 6.1% |
| Age 10 to 14 | 7.5% | 7.6% | 6.6% |
| Age 15 to 17 | 4.7% | 4.4% | 3.9% |
| Age 18 to 20 | 3.2% | 7.0% | 4.0% |
| Age 21 to 24 | 3.6% | 7.1% | 5.2% |
| Age 25 to 34 | 7.4% | 15.9% | 13.8% |
| Age 35 to 44 | 12.7% | 13.4% | 12.9% |
| Age 45 to 54 | 13.9% | 11.8% | 12.6% |
| Age 55 to 59 | 8.9% | 5.3% | 6.7% |
| Age 60 to 64 | 6.4% | 4.6% | 6.3% |
| Age 65 to 74 | 9.1% | 6.6% | 9.6% |
| Age 75 to 84 | 6.2% | 2.8% | 4.5% |
| Age 85 and over | 3.7% | 1.2% | 1.9% |
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| Race | | | |
| | Lemont, IL | Riverside, CA | United States |
| White | 89.1% | 27.6% | 59.4% |
| Black | 0.5% | 5.4% | 12.2% |
| Asian | 2.0% | 8.5% | 5.6% |
| Native American | 0.0% | 0.2% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.3% | 0.2% |
| Other | 0.0% | 0.3% | 0.4% |
| Two or More Races | 1.4% | 2.8% | 3.2% |
| Hispanic | 7.0% | 54.9% | 18.4% |
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| Marriage & Family | | | |
| | Lemont, IL | Riverside, CA | United States |
| Married Population | 61.6% | 44.4% | 49.8% |
| Currently Married | 60.7% | 42.3% | 48.0% |
| Married but Separated | 0.9% | 2.1% | 1.8% |
| Single Population | 38.4% | 55.6% | 50.2% |
| Never Married | 24.8% | 42.9% | 33.8% |
| Divorced | 7.5% | 8.4% | 10.8% |
| Widowed | 6.2% | 4.3% | 5.6% |
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| Household Size | 2.83 | 3.38 | 2.60 |
| Households | 6,119 | 88,340 | 124,010,992 |
| Family Households | 4,736 | 65,020 | 80,755,759 |
| Married couple, w/children | 40.0% | 36.3% | 30.5% |
| Married couple, no children | 46.0% | 32.9% | 42.9% |
| Non Family Households | 1,383 | 23,320 | 43,255,233 |
| Single householder, w/children | 8.7% | 17.7% | 15.8% |
| Single householder, no children | 5.3% | 13.1% | 10.8% |