| | Memphis, TN | Round Lake, IL | United States |
| Population | 634,139 | 18,720 | 329,725,481 |
| Female Population | 52.6% | 52.1% | 50.5% |
| Male Population | 47.4% | 47.9% | 49.5% |
| Median Age | 34.2 | 37 | 38.4 |
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| Population - 2010 | 652,349 | 18,378 | 309,327,143 |
| Population - 2000 | 650,100 | 5,842 | 285,036,114 |
| Population - 1990 | 610,337 | 3,550 | 251,960,433 |
| Pop. 2000 to Now | -0.1% | 207.8% | 15.6% |
| Pop. 1990 to Now | 6.5% | 406.5% | 30.8% |
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| Population Density | 1,998.1 | 3,367.5 | 93.4 |
| Land Area | 317.4 | 5.6 | 3,531,905.4 |
| Water Area | 9.0 | 0.2 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Memphis, TN | Round Lake, IL | United States |
| Age 0 to 4 | 7.4% | 6.1% | 5.9% |
| Age 5 to 9 | 6.8% | 8.5% | 6.1% |
| Age 10 to 14 | 6.9% | 8.0% | 6.6% |
| Age 15 to 17 | 3.8% | 6.2% | 3.9% |
| Age 18 to 20 | 4.0% | 4.1% | 4.0% |
| Age 21 to 24 | 6.1% | 5.6% | 5.2% |
| Age 25 to 34 | 16.1% | 8.0% | 13.8% |
| Age 35 to 44 | 12.1% | 17.8% | 12.9% |
| Age 45 to 54 | 11.3% | 15.7% | 12.6% |
| Age 55 to 59 | 5.8% | 4.7% | 6.7% |
| Age 60 to 64 | 6.2% | 5.3% | 6.3% |
| Age 65 to 74 | 8.4% | 7.2% | 9.6% |
| Age 75 to 84 | 3.7% | 1.8% | 4.5% |
| Age 85 and over | 1.4% | 0.8% | 1.9% |
| space1 | | | |
| Race | | | |
| | Memphis, TN | Round Lake, IL | United States |
| White | 24.3% | 51.5% | 59.4% |
| Black | 64.4% | 4.5% | 12.2% |
| Asian | 1.7% | 12.3% | 5.6% |
| Native American | 0.1% | 0.4% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.3% | 1.2% | 0.4% |
| Two or More Races | 1.5% | 3.5% | 3.2% |
| Hispanic | 7.7% | 26.8% | 18.4% |
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| Marriage & Family | | | |
| | Memphis, TN | Round Lake, IL | United States |
| Married Population | 34.8% | 54.3% | 49.8% |
| Currently Married | 31.4% | 53.5% | 48.0% |
| Married but Separated | 3.4% | 0.8% | 1.8% |
| Single Population | 65.2% | 45.7% | 50.2% |
| Never Married | 48.1% | 31.9% | 33.8% |
| Divorced | 11.3% | 10.7% | 10.8% |
| Widowed | 5.7% | 3.1% | 5.6% |
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| Household Size | 2.48 | 3.06 | 2.60 |
| Households | 249,554 | 6,117 | 124,010,992 |
| Family Households | 137,746 | 4,595 | 80,755,759 |
| Married couple, w/children | 18.9% | 42.8% | 30.5% |
| Married couple, no children | 31.7% | 38.5% | 42.9% |
| Non Family Households | 111,808 | 1,522 | 43,255,233 |
| Single householder, w/children | 31.5% | 13.2% | 15.8% |
| Single householder, no children | 17.9% | 5.4% | 10.8% |