| | Montross, VA | Ashburn, VA | United States |
| Population | 438 | 44,950 | 329,725,481 |
| Female Population | 49.8% | 52.2% | 50.5% |
| Male Population | 50.2% | 47.9% | 49.5% |
| Median Age | 40.8 | 40.4 | 38.4 |
| space3 | | | |
| Population - 2010 | 384 | 42,369 | 309,327,143 |
| Population - 2000 | 315 | 26,428 | 285,036,114 |
| Population - 1990 | 359 | 3,393 | 251,960,433 |
| Pop. 2000 to Now | 24.4% | 113.3% | 15.6% |
| Pop. 1990 to Now | 9.2% | 1,561.6% | 30.8% |
| space4 | | | |
| Population Density | 424.8 | 2,616.1 | 93.4 |
| Land Area | 1.0 | 17.2 | 3,531,905.4 |
| Water Area | 0.0 | 0.3 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Montross, VA | Ashburn, VA | United States |
| Age 0 to 4 | 6.8% | 5.5% | 5.9% |
| Age 5 to 9 | 8.0% | 6.4% | 6.1% |
| Age 10 to 14 | 2.5% | 7.4% | 6.6% |
| Age 15 to 17 | 0.0% | 4.1% | 3.9% |
| Age 18 to 20 | 0.0% | 3.3% | 4.0% |
| Age 21 to 24 | 3.9% | 4.3% | 5.2% |
| Age 25 to 34 | 11.9% | 11.5% | 13.8% |
| Age 35 to 44 | 24.0% | 13.5% | 12.9% |
| Age 45 to 54 | 3.0% | 16.1% | 12.6% |
| Age 55 to 59 | 3.7% | 6.8% | 6.7% |
| Age 60 to 64 | 4.6% | 5.4% | 6.3% |
| Age 65 to 74 | 20.8% | 7.2% | 9.6% |
| Age 75 to 84 | 7.8% | 5.8% | 4.5% |
| Age 85 and over | 3.2% | 2.8% | 1.9% |
| space1 | | | |
| Race | | | |
| | Montross, VA | Ashburn, VA | United States |
| White | 74.2% | 57.6% | 59.4% |
| Black | 15.3% | 6.7% | 12.2% |
| Asian | 5.5% | 20.2% | 5.6% |
| Native American | 0.0% | 0.1% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.1% | 0.2% |
| Other | 0.0% | 0.4% | 0.4% |
| Two or More Races | 5.0% | 4.6% | 3.2% |
| Hispanic | 0.0% | 10.2% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Montross, VA | Ashburn, VA | United States |
| Married Population | 51.9% | 60.4% | 49.8% |
| Currently Married | 50.6% | 59.1% | 48.0% |
| Married but Separated | 1.4% | 1.4% | 1.8% |
| Single Population | 48.1% | 39.6% | 50.2% |
| Never Married | 29.6% | 25.3% | 33.8% |
| Divorced | 6.9% | 8.5% | 10.8% |
| Widowed | 11.6% | 5.7% | 5.6% |
| space5 | | | |
| Household Size | 2.47 | 2.70 | 2.60 |
| Households | 177 | 16,627 | 124,010,992 |
| Family Households | 95 | 11,438 | 80,755,759 |
| Married couple, w/children | 33.7% | 42.8% | 30.5% |
| Married couple, no children | 52.6% | 45.0% | 42.9% |
| Non Family Households | 82 | 5,189 | 43,255,233 |
| Single householder, w/children | 3.2% | 7.2% | 15.8% |
| Single householder, no children | 10.5% | 4.9% | 10.8% |