| | Jarrettsville, MD | Littleton, CO | United States |
| Population | 2,751 | 45,465 | 329,725,481 |
| Female Population | 49.5% | 50.9% | 50.5% |
| Male Population | 50.5% | 49.2% | 49.5% |
| Median Age | 43.8 | 40.1 | 38.4 |
| space3 | | | |
| Population - 2010 | 3,152 | 41,598 | 309,327,143 |
| Population - 2000 | 2,756 | 40,340 | 285,036,114 |
| Population - 1990 | 2,148 | 33,685 | 251,960,433 |
| Pop. 2000 to Now | 21.5% | 14.0% | 15.6% |
| Pop. 1990 to Now | 55.9% | 36.6% | 30.8% |
| space4 | | | |
| Population Density | 318.6 | 3,609.2 | 93.4 |
| Land Area | 8.6 | 12.6 | 3,531,905.4 |
| Water Area | 0.0 | 1.1 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Jarrettsville, MD | Littleton, CO | United States |
| Age 0 to 4 | 4.9% | 4.7% | 5.9% |
| Age 5 to 9 | 7.5% | 5.8% | 6.1% |
| Age 10 to 14 | 6.2% | 5.2% | 6.6% |
| Age 15 to 17 | 3.7% | 2.6% | 3.9% |
| Age 18 to 20 | 1.1% | 2.2% | 4.0% |
| Age 21 to 24 | 3.4% | 4.7% | 5.2% |
| Age 25 to 34 | 9.3% | 17.6% | 13.8% |
| Age 35 to 44 | 15.3% | 13.4% | 12.9% |
| Age 45 to 54 | 9.7% | 10.7% | 12.6% |
| Age 55 to 59 | 10.3% | 7.2% | 6.7% |
| Age 60 to 64 | 7.5% | 7.4% | 6.3% |
| Age 65 to 74 | 12.7% | 10.4% | 9.6% |
| Age 75 to 84 | 7.0% | 5.0% | 4.5% |
| Age 85 and over | 1.6% | 2.8% | 1.9% |
| space1 | | | |
| Race | | | |
| | Jarrettsville, MD | Littleton, CO | United States |
| White | 90.1% | 80.4% | 59.4% |
| Black | 1.7% | 2.4% | 12.2% |
| Asian | 0.5% | 2.4% | 5.6% |
| Native American | 0.0% | 0.1% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 1.6% | 0.1% | 0.4% |
| Two or More Races | 2.9% | 2.0% | 3.2% |
| Hispanic | 3.3% | 12.5% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Jarrettsville, MD | Littleton, CO | United States |
| Married Population | 72.0% | 51.4% | 49.8% |
| Currently Married | 72.0% | 50.4% | 48.0% |
| Married but Separated | 0.0% | 1.0% | 1.8% |
| Single Population | 28.0% | 48.6% | 50.2% |
| Never Married | 16.0% | 28.9% | 33.8% |
| Divorced | 5.9% | 14.5% | 10.8% |
| Widowed | 6.1% | 5.2% | 5.6% |
| space5 | | | |
| Household Size | 2.80 | 2.23 | 2.60 |
| Households | 982 | 20,126 | 124,010,992 |
| Family Households | 787 | 11,523 | 80,755,759 |
| Married couple, w/children | 31.0% | 29.9% | 30.5% |
| Married couple, no children | 65.3% | 49.0% | 42.9% |
| Non Family Households | 195 | 8,603 | 43,255,233 |
| Single householder, w/children | 0.0% | 11.0% | 15.8% |
| Single householder, no children | 3.7% | 10.1% | 10.8% |