| | Houston, TX | Rock Island, IL | United States |
| Population | 2,293,288 | 37,519 | 329,725,481 |
| Female Population | 50.2% | 50.0% | 50.5% |
| Male Population | 49.8% | 50.0% | 49.5% |
| Median Age | 33.7 | 35.4 | 38.4 |
| space3 | | | |
| Population - 2010 | 2,097,647 | 38,973 | 309,327,143 |
| Population - 2000 | 1,953,631 | 39,684 | 285,036,114 |
| Population - 1990 | 1,630,553 | 40,552 | 251,960,433 |
| Pop. 2000 to Now | 18.6% | -7.1% | 15.6% |
| Pop. 1990 to Now | 42.1% | -9.1% | 30.8% |
| space4 | | | |
| Population Density | 3,600.4 | 2,226.0 | 93.4 |
| Land Area | 637.0 | 16.9 | 3,531,905.4 |
| Water Area | 29.4 | 0.2 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Houston, TX | Rock Island, IL | United States |
| Age 0 to 4 | 7.2% | 6.2% | 5.9% |
| Age 5 to 9 | 6.7% | 5.3% | 6.1% |
| Age 10 to 14 | 6.8% | 6.9% | 6.6% |
| Age 15 to 17 | 3.9% | 3.9% | 3.9% |
| Age 18 to 20 | 3.8% | 8.5% | 4.0% |
| Age 21 to 24 | 5.9% | 5.9% | 5.2% |
| Age 25 to 34 | 18.0% | 12.8% | 13.8% |
| Age 35 to 44 | 14.3% | 11.4% | 12.9% |
| Age 45 to 54 | 11.8% | 9.9% | 12.6% |
| Age 55 to 59 | 5.5% | 5.7% | 6.7% |
| Age 60 to 64 | 5.1% | 6.3% | 6.3% |
| Age 65 to 74 | 6.8% | 10.0% | 9.6% |
| Age 75 to 84 | 3.0% | 4.5% | 4.5% |
| Age 85 and over | 1.3% | 2.5% | 1.9% |
| space1 | | | |
| Race | | | |
| | Houston, TX | Rock Island, IL | United States |
| White | 24.1% | 61.1% | 59.4% |
| Black | 22.1% | 17.1% | 12.2% |
| Asian | 6.7% | 4.5% | 5.6% |
| Native American | 0.1% | 0.2% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.1% | 0.2% |
| Other | 0.3% | 0.1% | 0.4% |
| Two or More Races | 2.0% | 3.2% | 3.2% |
| Hispanic | 44.5% | 13.7% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Houston, TX | Rock Island, IL | United States |
| Married Population | 44.2% | 39.4% | 49.8% |
| Currently Married | 41.2% | 37.6% | 48.0% |
| Married but Separated | 3.0% | 1.8% | 1.8% |
| Single Population | 55.8% | 60.6% | 50.2% |
| Never Married | 41.1% | 41.2% | 33.8% |
| Divorced | 10.2% | 12.6% | 10.8% |
| Widowed | 4.5% | 6.7% | 5.6% |
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| Household Size | 2.57 | 2.26 | 2.60 |
| Households | 878,906 | 15,285 | 124,010,992 |
| Family Households | 526,606 | 7,918 | 80,755,759 |
| Married couple, w/children | 29.8% | 27.4% | 30.5% |
| Married couple, no children | 32.8% | 39.9% | 42.9% |
| Non Family Households | 352,300 | 7,367 | 43,255,233 |
| Single householder, w/children | 22.5% | 21.8% | 15.8% |
| Single householder, no children | 14.9% | 10.8% | 10.8% |