| | Rockland, NY | Ellicott City, MD | United States |
| Population | 3,346 | 74,432 | 329,725,481 |
| Female Population | 53.8% | 51.2% | 50.5% |
| Male Population | 46.2% | 48.8% | 49.5% |
| Median Age | 50.7 | 41.8 | 38.4 |
| space3 | | | |
| Population - 2010 | 3,748 | 64,970 | 309,327,143 |
| Population - 2000 | 3,913 | 56,397 | 285,036,114 |
| Population - 1990 | 4,096 | 41,396 | 251,960,433 |
| Pop. 2000 to Now | -5.9% | 34.1% | 15.6% |
| Pop. 1990 to Now | -10.1% | 82.6% | 30.8% |
| space4 | | | |
| Population Density | 35.5 | 2,484.0 | 93.4 |
| Land Area | 94.2 | 30.0 | 3,531,905.4 |
| Water Area | 1.1 | 0.1 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Rockland, NY | Ellicott City, MD | United States |
| Age 0 to 4 | 6.4% | 5.1% | 5.9% |
| Age 5 to 9 | 5.2% | 7.0% | 6.1% |
| Age 10 to 14 | 4.7% | 8.7% | 6.6% |
| Age 15 to 17 | 3.9% | 5.2% | 3.9% |
| Age 18 to 20 | 3.5% | 3.2% | 4.0% |
| Age 21 to 24 | 2.8% | 3.5% | 5.2% |
| Age 25 to 34 | 9.3% | 8.0% | 13.8% |
| Age 35 to 44 | 7.1% | 14.7% | 12.9% |
| Age 45 to 54 | 14.6% | 15.3% | 12.6% |
| Age 55 to 59 | 6.0% | 7.0% | 6.7% |
| Age 60 to 64 | 6.1% | 5.8% | 6.3% |
| Age 65 to 74 | 21.9% | 10.2% | 9.6% |
| Age 75 to 84 | 6.8% | 4.3% | 4.5% |
| Age 85 and over | 1.6% | 2.0% | 1.9% |
| space1 | | | |
| Race | | | |
| | Rockland, NY | Ellicott City, MD | United States |
| White | 83.0% | 52.6% | 59.4% |
| Black | 0.2% | 8.1% | 12.2% |
| Asian | 1.0% | 29.6% | 5.6% |
| Native American | 0.0% | 0.2% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.6% | 0.4% |
| Two or More Races | 7.3% | 4.4% | 3.2% |
| Hispanic | 8.4% | 4.6% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Rockland, NY | Ellicott City, MD | United States |
| Married Population | 46.9% | 64.0% | 49.8% |
| Currently Married | 46.9% | 63.1% | 48.0% |
| Married but Separated | 0.0% | 1.0% | 1.8% |
| Single Population | 53.1% | 36.0% | 50.2% |
| Never Married | 30.5% | 24.7% | 33.8% |
| Divorced | 13.5% | 6.4% | 10.8% |
| Widowed | 9.1% | 4.9% | 5.6% |
| space5 | | | |
| Household Size | 2.09 | 2.77 | 2.60 |
| Households | 1,589 | 26,737 | 124,010,992 |
| Family Households | 741 | 20,460 | 80,755,759 |
| Married couple, w/children | 33.9% | 45.2% | 30.5% |
| Married couple, no children | 47.8% | 40.5% | 42.9% |
| Non Family Households | 848 | 6,277 | 43,255,233 |
| Single householder, w/children | 12.7% | 8.5% | 15.8% |
| Single householder, no children | 5.7% | 5.8% | 10.8% |