| | Triangle, VA | Mechanicsville, VA | United States |
| Population | 10,868 | 37,767 | 329,725,481 |
| Female Population | 45.7% | 51.1% | 50.5% |
| Male Population | 54.3% | 49.0% | 49.5% |
| Median Age | 33.6 | 41.7 | 38.4 |
| space3 | | | |
| Population - 2010 | 7,693 | 35,628 | 309,327,143 |
| Population - 2000 | 5,500 | 30,464 | 285,036,114 |
| Population - 1990 | 4,740 | 22,027 | 251,960,433 |
| Pop. 2000 to Now | 71.9% | 29.9% | 15.6% |
| Pop. 1990 to Now | 99.5% | 79.6% | 30.8% |
| space4 | | | |
| Population Density | 3,860.8 | 1,332.3 | 93.4 |
| Land Area | 2.8 | 28.3 | 3,531,905.4 |
| Water Area | 0.2 | 0.1 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Triangle, VA | Mechanicsville, VA | United States |
| Age 0 to 4 | 7.7% | 5.3% | 5.9% |
| Age 5 to 9 | 4.7% | 5.2% | 6.1% |
| Age 10 to 14 | 5.8% | 7.8% | 6.6% |
| Age 15 to 17 | 6.3% | 4.5% | 3.9% |
| Age 18 to 20 | 6.2% | 4.4% | 4.0% |
| Age 21 to 24 | 4.7% | 3.3% | 5.2% |
| Age 25 to 34 | 16.6% | 10.8% | 13.8% |
| Age 35 to 44 | 15.0% | 12.4% | 12.9% |
| Age 45 to 54 | 14.0% | 12.8% | 12.6% |
| Age 55 to 59 | 5.8% | 7.4% | 6.7% |
| Age 60 to 64 | 6.5% | 7.2% | 6.3% |
| Age 65 to 74 | 3.4% | 10.3% | 9.6% |
| Age 75 to 84 | 2.2% | 5.6% | 4.5% |
| Age 85 and over | 1.0% | 3.0% | 1.9% |
| space1 | | | |
| Race | | | |
| | Triangle, VA | Mechanicsville, VA | United States |
| White | 19.7% | 83.0% | 59.4% |
| Black | 37.6% | 8.5% | 12.2% |
| Asian | 13.7% | 1.6% | 5.6% |
| Native American | 0.0% | 0.1% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.1% | 0.2% |
| Other | 0.5% | 0.4% | 0.4% |
| Two or More Races | 3.6% | 4.6% | 3.2% |
| Hispanic | 25.0% | 1.8% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Triangle, VA | Mechanicsville, VA | United States |
| Married Population | 52.4% | 53.2% | 49.8% |
| Currently Married | 50.3% | 51.1% | 48.0% |
| Married but Separated | 2.1% | 2.2% | 1.8% |
| Single Population | 47.6% | 46.8% | 50.2% |
| Never Married | 37.1% | 27.4% | 33.8% |
| Divorced | 8.1% | 12.1% | 10.8% |
| Widowed | 2.4% | 7.3% | 5.6% |
| space5 | | | |
| Household Size | 3.33 | 2.56 | 2.60 |
| Households | 3,262 | 14,675 | 124,010,992 |
| Family Households | 2,379 | 9,875 | 80,755,759 |
| Married couple, w/children | 46.2% | 30.1% | 30.5% |
| Married couple, no children | 30.3% | 46.5% | 42.9% |
| Non Family Households | 883 | 4,800 | 43,255,233 |
| Single householder, w/children | 14.8% | 14.4% | 15.8% |
| Single householder, no children | 8.7% | 8.9% | 10.8% |