| | Rockwall, TX | McKinney, TX | United States |
| Population | 46,150 | 189,394 | 329,725,481 |
| Female Population | 49.9% | 50.7% | 50.5% |
| Male Population | 50.1% | 49.3% | 49.5% |
| Median Age | 38.3 | 36.9 | 38.4 |
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| Population - 2010 | 37,954 | 132,940 | 309,327,143 |
| Population - 2000 | 17,976 | 54,369 | 285,036,114 |
| Population - 1990 | 10,486 | 21,283 | 251,960,433 |
| Pop. 2000 to Now | 163.8% | 283.1% | 15.6% |
| Pop. 1990 to Now | 352.2% | 878.6% | 30.8% |
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| Population Density | 1,572.3 | 2,829.6 | 93.4 |
| Land Area | 29.4 | 66.9 | 3,531,905.4 |
| Water Area | 0.5 | 0.7 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Rockwall, TX | McKinney, TX | United States |
| Age 0 to 4 | 6.1% | 6.7% | 5.9% |
| Age 5 to 9 | 5.7% | 8.6% | 6.1% |
| Age 10 to 14 | 7.2% | 8.7% | 6.6% |
| Age 15 to 17 | 5.6% | 4.7% | 3.9% |
| Age 18 to 20 | 4.7% | 3.6% | 4.0% |
| Age 21 to 24 | 4.4% | 3.9% | 5.2% |
| Age 25 to 34 | 11.8% | 11.1% | 13.8% |
| Age 35 to 44 | 14.1% | 18.0% | 12.9% |
| Age 45 to 54 | 15.7% | 14.6% | 12.6% |
| Age 55 to 59 | 7.4% | 5.8% | 6.7% |
| Age 60 to 64 | 4.1% | 4.3% | 6.3% |
| Age 65 to 74 | 7.7% | 5.9% | 9.6% |
| Age 75 to 84 | 4.2% | 3.0% | 4.5% |
| Age 85 and over | 1.3% | 1.1% | 1.9% |
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| Race | | | |
| | Rockwall, TX | McKinney, TX | United States |
| White | 69.6% | 56.8% | 59.4% |
| Black | 7.5% | 11.8% | 12.2% |
| Asian | 4.0% | 10.7% | 5.6% |
| Native American | 0.1% | 0.3% | 0.6% |
| Hawaiian, Pacific Islander | 0.1% | 0.0% | 0.2% |
| Other | 0.6% | 0.3% | 0.4% |
| Two or More Races | 2.4% | 3.2% | 3.2% |
| Hispanic | 15.6% | 16.9% | 18.4% |
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| Marriage & Family | | | |
| | Rockwall, TX | McKinney, TX | United States |
| Married Population | 62.7% | 61.4% | 49.8% |
| Currently Married | 61.6% | 60.1% | 48.0% |
| Married but Separated | 1.1% | 1.3% | 1.8% |
| Single Population | 37.3% | 38.6% | 50.2% |
| Never Married | 25.4% | 25.9% | 33.8% |
| Divorced | 8.0% | 9.1% | 10.8% |
| Widowed | 3.9% | 3.6% | 5.6% |
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| Household Size | 2.80 | 2.86 | 2.60 |
| Households | 16,395 | 65,770 | 124,010,992 |
| Family Households | 13,267 | 50,446 | 80,755,759 |
| Married couple, w/children | 43.3% | 45.7% | 30.5% |
| Married couple, no children | 41.2% | 35.7% | 42.9% |
| Non Family Households | 3,128 | 15,324 | 43,255,233 |
| Single householder, w/children | 9.9% | 12.3% | 15.8% |
| Single householder, no children | 5.5% | 6.2% | 10.8% |