| | Mercersburg, PA | Morgan Hill, CA | United States |
| Population | 1,724 | 45,267 | 329,725,481 |
| Female Population | 52.9% | 52.6% | 50.5% |
| Male Population | 47.1% | 47.4% | 49.5% |
| Median Age | 46.3 | 38.5 | 38.4 |
| space3 | | | |
| Population - 2010 | 1,549 | 38,103 | 309,327,143 |
| Population - 2000 | 1,540 | 33,556 | 285,036,114 |
| Population - 1990 | 1,640 | 23,928 | 251,960,433 |
| Pop. 2000 to Now | -0.8% | 35.6% | 15.6% |
| Pop. 1990 to Now | -6.9% | 90.2% | 30.8% |
| space4 | | | |
| Population Density | 1,911.3 | 3,545.1 | 93.4 |
| Land Area | 0.9 | 12.8 | 3,531,905.4 |
| Water Area | 0.0 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Mercersburg, PA | Morgan Hill, CA | United States |
| Age 0 to 4 | 5.9% | 7.2% | 5.9% |
| Age 5 to 9 | 2.3% | 6.4% | 6.1% |
| Age 10 to 14 | 6.6% | 8.6% | 6.6% |
| Age 15 to 17 | 3.1% | 3.8% | 3.9% |
| Age 18 to 20 | 4.5% | 2.8% | 4.0% |
| Age 21 to 24 | 3.2% | 4.4% | 5.2% |
| Age 25 to 34 | 11.1% | 12.2% | 13.8% |
| Age 35 to 44 | 12.2% | 13.8% | 12.9% |
| Age 45 to 54 | 17.7% | 13.5% | 12.6% |
| Age 55 to 59 | 9.2% | 7.4% | 6.7% |
| Age 60 to 64 | 5.8% | 6.4% | 6.3% |
| Age 65 to 74 | 9.0% | 8.3% | 9.6% |
| Age 75 to 84 | 6.7% | 3.8% | 4.5% |
| Age 85 and over | 2.7% | 1.4% | 1.9% |
| space1 | | | |
| Race | | | |
| | Mercersburg, PA | Morgan Hill, CA | United States |
| White | 84.6% | 44.1% | 59.4% |
| Black | 7.8% | 1.3% | 12.2% |
| Asian | 0.6% | 15.5% | 5.6% |
| Native American | 0.0% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.3% | 0.4% |
| Two or More Races | 3.0% | 4.0% | 3.2% |
| Hispanic | 4.1% | 34.7% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Mercersburg, PA | Morgan Hill, CA | United States |
| Married Population | 47.8% | 59.5% | 49.8% |
| Currently Married | 40.2% | 58.4% | 48.0% |
| Married but Separated | 7.6% | 1.1% | 1.8% |
| Single Population | 52.2% | 40.5% | 50.2% |
| Never Married | 29.2% | 27.7% | 33.8% |
| Divorced | 15.4% | 9.4% | 10.8% |
| Widowed | 7.6% | 3.5% | 5.6% |
| space5 | | | |
| Household Size | 2.32 | 3.05 | 2.60 |
| Households | 742 | 14,721 | 124,010,992 |
| Family Households | 422 | 11,793 | 80,755,759 |
| Married couple, w/children | 24.9% | 38.7% | 30.5% |
| Married couple, no children | 37.9% | 40.8% | 42.9% |
| Non Family Households | 320 | 2,928 | 43,255,233 |
| Single householder, w/children | 20.6% | 11.2% | 15.8% |
| Single householder, no children | 16.6% | 9.2% | 10.8% |