| | Londonderry, NH | Harrisonburg, VA | United States |
| Population | 25,708 | 52,062 | 329,725,481 |
| Female Population | 50.0% | 51.3% | 50.5% |
| Male Population | 50.0% | 48.7% | 49.5% |
| Median Age | 42.2 | 25.5 | 38.4 |
| space3 | | | |
| Population - 2010 | 24,024 | 48,999 | 309,327,143 |
| Population - 2000 | 23,236 | 40,468 | 285,036,114 |
| Population - 1990 | 19,781 | 30,707 | 251,960,433 |
| Pop. 2000 to Now | 14.7% | 31.5% | 15.6% |
| Pop. 1990 to Now | 34.7% | 73.3% | 30.8% |
| space4 | | | |
| Population Density | 612.3 | 3,002.6 | 93.4 |
| Land Area | 42.0 | 17.3 | 3,531,905.4 |
| Water Area | 0.1 | 0.1 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Londonderry, NH | Harrisonburg, VA | United States |
| Age 0 to 4 | 5.4% | 4.7% | 5.9% |
| Age 5 to 9 | 4.8% | 5.1% | 6.1% |
| Age 10 to 14 | 5.9% | 4.1% | 6.6% |
| Age 15 to 17 | 5.8% | 2.5% | 3.9% |
| Age 18 to 20 | 4.7% | 19.1% | 4.0% |
| Age 21 to 24 | 5.6% | 13.4% | 5.2% |
| Age 25 to 34 | 9.8% | 13.8% | 13.8% |
| Age 35 to 44 | 12.2% | 10.8% | 12.9% |
| Age 45 to 54 | 15.6% | 9.0% | 12.6% |
| Age 55 to 59 | 9.0% | 4.6% | 6.7% |
| Age 60 to 64 | 5.9% | 3.7% | 6.3% |
| Age 65 to 74 | 10.1% | 5.3% | 9.6% |
| Age 75 to 84 | 4.3% | 2.5% | 4.5% |
| Age 85 and over | 0.9% | 1.2% | 1.9% |
| space1 | | | |
| Race | | | |
| | Londonderry, NH | Harrisonburg, VA | United States |
| White | 91.4% | 64.3% | 59.4% |
| Black | 1.4% | 6.6% | 12.2% |
| Asian | 1.8% | 3.1% | 5.6% |
| Native American | 0.1% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.1% | 0.0% | 0.2% |
| Other | 0.0% | 0.7% | 0.4% |
| Two or More Races | 1.5% | 4.9% | 3.2% |
| Hispanic | 3.7% | 20.5% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Londonderry, NH | Harrisonburg, VA | United States |
| Married Population | 58.5% | 31.3% | 49.8% |
| Currently Married | 57.9% | 29.0% | 48.0% |
| Married but Separated | 0.6% | 2.3% | 1.8% |
| Single Population | 41.5% | 68.7% | 50.2% |
| Never Married | 28.0% | 57.7% | 33.8% |
| Divorced | 9.8% | 7.8% | 10.8% |
| Widowed | 3.7% | 3.2% | 5.6% |
| space5 | | | |
| Household Size | 2.74 | 2.63 | 2.60 |
| Households | 9,369 | 17,102 | 124,010,992 |
| Family Households | 7,239 | 9,258 | 80,755,759 |
| Married couple, w/children | 35.9% | 33.2% | 30.5% |
| Married couple, no children | 45.7% | 31.0% | 42.9% |
| Non Family Households | 2,130 | 7,844 | 43,255,233 |
| Single householder, w/children | 11.6% | 20.4% | 15.8% |
| Single householder, no children | 6.7% | 15.5% | 10.8% |