| | Hagerstown, MD | Louisville, CO | United States |
| Population | 43,015 | 21,091 | 329,725,481 |
| Female Population | 52.4% | 49.4% | 50.5% |
| Male Population | 47.7% | 50.6% | 49.5% |
| Median Age | 35.6 | 42.5 | 38.4 |
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| Population - 2010 | 39,680 | 18,412 | 309,327,143 |
| Population - 2000 | 36,687 | 18,937 | 285,036,114 |
| Population - 1990 | 35,445 | 12,361 | 251,960,433 |
| Pop. 2000 to Now | 8.8% | 0.7% | 15.6% |
| Pop. 1990 to Now | 12.6% | 54.2% | 30.8% |
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| Population Density | 3,535.7 | 2,644.0 | 93.4 |
| Land Area | 12.2 | 8.0 | 3,531,905.4 |
| Water Area | 0.0 | 0.1 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Hagerstown, MD | Louisville, CO | United States |
| Age 0 to 4 | 7.8% | 4.5% | 5.9% |
| Age 5 to 9 | 8.4% | 6.8% | 6.1% |
| Age 10 to 14 | 6.3% | 8.0% | 6.6% |
| Age 15 to 17 | 3.8% | 4.3% | 3.9% |
| Age 18 to 20 | 3.0% | 2.8% | 4.0% |
| Age 21 to 24 | 4.4% | 3.4% | 5.2% |
| Age 25 to 34 | 15.3% | 11.2% | 13.8% |
| Age 35 to 44 | 12.2% | 13.0% | 12.9% |
| Age 45 to 54 | 13.1% | 15.1% | 12.6% |
| Age 55 to 59 | 5.6% | 8.6% | 6.7% |
| Age 60 to 64 | 5.7% | 8.0% | 6.3% |
| Age 65 to 74 | 7.8% | 9.0% | 9.6% |
| Age 75 to 84 | 4.7% | 3.0% | 4.5% |
| Age 85 and over | 1.8% | 2.3% | 1.9% |
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| Race | | | |
| | Hagerstown, MD | Louisville, CO | United States |
| White | 63.1% | 82.3% | 59.4% |
| Black | 17.8% | 0.6% | 12.2% |
| Asian | 1.9% | 4.1% | 5.6% |
| Native American | 0.1% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.2% | 0.0% | 0.2% |
| Other | 0.4% | 0.1% | 0.4% |
| Two or More Races | 7.8% | 4.0% | 3.2% |
| Hispanic | 8.8% | 8.8% | 18.4% |
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| Marriage & Family | | | |
| | Hagerstown, MD | Louisville, CO | United States |
| Married Population | 40.5% | 56.9% | 49.8% |
| Currently Married | 37.4% | 56.6% | 48.0% |
| Married but Separated | 3.1% | 0.3% | 1.8% |
| Single Population | 59.5% | 43.1% | 50.2% |
| Never Married | 37.3% | 27.8% | 33.8% |
| Divorced | 16.0% | 10.9% | 10.8% |
| Widowed | 6.3% | 4.4% | 5.6% |
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| Household Size | 2.29 | 2.50 | 2.60 |
| Households | 18,372 | 8,400 | 124,010,992 |
| Family Households | 9,994 | 5,519 | 80,755,759 |
| Married couple, w/children | 26.6% | 38.7% | 30.5% |
| Married couple, no children | 30.0% | 43.2% | 42.9% |
| Non Family Households | 8,378 | 2,881 | 43,255,233 |
| Single householder, w/children | 31.5% | 12.2% | 15.8% |
| Single householder, no children | 12.0% | 5.9% | 10.8% |