| | Hermann, MO | Washington, MO | United States |
| Population | 2,347 | 14,607 | 329,725,481 |
| Female Population | 52.9% | 53.4% | 50.5% |
| Male Population | 47.1% | 46.6% | 49.5% |
| Median Age | 48.3 | 39.6 | 38.4 |
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| Population - 2010 | 2,435 | 13,973 | 309,327,143 |
| Population - 2000 | 2,674 | 13,243 | 285,036,114 |
| Population - 1990 | 2,754 | 10,704 | 251,960,433 |
| Pop. 2000 to Now | -13.2% | 7.6% | 15.6% |
| Pop. 1990 to Now | -15.7% | 33.1% | 30.8% |
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| Population Density | 928.8 | 1,546.5 | 93.4 |
| Land Area | 2.5 | 9.4 | 3,531,905.4 |
| Water Area | 0.2 | 0.5 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Hermann, MO | Washington, MO | United States |
| Age 0 to 4 | 5.4% | 6.2% | 5.9% |
| Age 5 to 9 | 5.5% | 4.5% | 6.1% |
| Age 10 to 14 | 6.2% | 5.9% | 6.6% |
| Age 15 to 17 | 2.4% | 5.4% | 3.9% |
| Age 18 to 20 | 2.6% | 5.3% | 4.0% |
| Age 21 to 24 | 0.8% | 4.5% | 5.2% |
| Age 25 to 34 | 10.7% | 13.0% | 13.8% |
| Age 35 to 44 | 12.6% | 12.1% | 12.9% |
| Age 45 to 54 | 13.6% | 12.8% | 12.6% |
| Age 55 to 59 | 7.5% | 6.3% | 6.7% |
| Age 60 to 64 | 6.6% | 6.3% | 6.3% |
| Age 65 to 74 | 14.1% | 9.8% | 9.6% |
| Age 75 to 84 | 9.7% | 6.0% | 4.5% |
| Age 85 and over | 2.3% | 2.1% | 1.9% |
| space1 | | | |
| Race | | | |
| | Hermann, MO | Washington, MO | United States |
| White | 93.0% | 94.7% | 59.4% |
| Black | 2.6% | 0.1% | 12.2% |
| Asian | 0.0% | 0.8% | 5.6% |
| Native American | 0.0% | 0.1% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.1% | 0.2% |
| Other | 0.9% | 0.5% | 0.4% |
| Two or More Races | 3.5% | 2.1% | 3.2% |
| Hispanic | 0.0% | 1.7% | 18.4% |
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| Marriage & Family | | | |
| | Hermann, MO | Washington, MO | United States |
| Married Population | 59.1% | 50.6% | 49.8% |
| Currently Married | 56.9% | 49.4% | 48.0% |
| Married but Separated | 2.3% | 1.1% | 1.8% |
| Single Population | 40.9% | 49.4% | 50.2% |
| Never Married | 16.9% | 31.7% | 33.8% |
| Divorced | 16.0% | 10.4% | 10.8% |
| Widowed | 8.0% | 7.3% | 5.6% |
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| Household Size | 2.27 | 2.39 | 2.60 |
| Households | 1,002 | 6,048 | 124,010,992 |
| Family Households | 573 | 3,804 | 80,755,759 |
| Married couple, w/children | 26.5% | 32.9% | 30.5% |
| Married couple, no children | 61.8% | 44.4% | 42.9% |
| Non Family Households | 429 | 2,244 | 43,255,233 |
| Single householder, w/children | 8.6% | 14.1% | 15.8% |
| Single householder, no children | 3.1% | 8.6% | 10.8% |