| | Watertown, WI | Beaver Dam, WI | United States |
| Population | 23,030 | 16,594 | 329,725,481 |
| Female Population | 52.0% | 45.5% | 50.5% |
| Male Population | 48.0% | 54.5% | 49.5% |
| Median Age | 39.4 | 40.1 | 38.4 |
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| Population - 2010 | 23,861 | 16,199 | 309,327,143 |
| Population - 2000 | 21,598 | 15,169 | 285,036,114 |
| Population - 1990 | 19,142 | 14,196 | 251,960,433 |
| Pop. 2000 to Now | 8.2% | 7.5% | 15.6% |
| Pop. 1990 to Now | 22.1% | 14.8% | 30.8% |
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| Population Density | 1,907.6 | 2,313.4 | 93.4 |
| Land Area | 12.1 | 7.2 | 3,531,905.4 |
| Water Area | 0.4 | 1.4 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Watertown, WI | Beaver Dam, WI | United States |
| Age 0 to 4 | 4.9% | 4.2% | 5.9% |
| Age 5 to 9 | 6.3% | 4.9% | 6.1% |
| Age 10 to 14 | 7.1% | 6.9% | 6.6% |
| Age 15 to 17 | 3.9% | 3.9% | 3.9% |
| Age 18 to 20 | 5.2% | 5.0% | 4.0% |
| Age 21 to 24 | 4.2% | 4.3% | 5.2% |
| Age 25 to 34 | 12.4% | 13.3% | 13.8% |
| Age 35 to 44 | 12.0% | 13.9% | 12.9% |
| Age 45 to 54 | 12.4% | 13.1% | 12.6% |
| Age 55 to 59 | 6.8% | 6.0% | 6.7% |
| Age 60 to 64 | 6.7% | 6.9% | 6.3% |
| Age 65 to 74 | 8.4% | 10.0% | 9.6% |
| Age 75 to 84 | 6.5% | 5.6% | 4.5% |
| Age 85 and over | 3.1% | 2.1% | 1.9% |
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| Race | | | |
| | Watertown, WI | Beaver Dam, WI | United States |
| White | 84.1% | 84.0% | 59.4% |
| Black | 1.4% | 2.2% | 12.2% |
| Asian | 0.3% | 1.5% | 5.6% |
| Native American | 0.1% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.1% | 0.0% | 0.4% |
| Two or More Races | 2.6% | 3.9% | 3.2% |
| Hispanic | 11.5% | 8.3% | 18.4% |
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| Marriage & Family | | | |
| | Watertown, WI | Beaver Dam, WI | United States |
| Married Population | 48.0% | 41.7% | 49.8% |
| Currently Married | 47.1% | 40.6% | 48.0% |
| Married but Separated | 0.9% | 1.2% | 1.8% |
| Single Population | 52.0% | 58.3% | 50.2% |
| Never Married | 31.8% | 35.8% | 33.8% |
| Divorced | 13.6% | 15.0% | 10.8% |
| Widowed | 6.7% | 7.5% | 5.6% |
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| Household Size | 2.46 | 2.18 | 2.60 |
| Households | 8,996 | 7,519 | 124,010,992 |
| Family Households | 5,748 | 3,917 | 80,755,759 |
| Married couple, w/children | 28.4% | 33.4% | 30.5% |
| Married couple, no children | 43.8% | 37.4% | 42.9% |
| Non Family Households | 3,248 | 3,602 | 43,255,233 |
| Single householder, w/children | 18.6% | 19.5% | 15.8% |
| Single householder, no children | 9.3% | 9.7% | 10.8% |