| | Three Rivers, CA | Santa Cruz, CA | United States |
| Population | 2,601 | 62,714 | 329,725,481 |
| Female Population | 42.8% | 50.9% | 50.5% |
| Male Population | 57.2% | 49.1% | 49.5% |
| Median Age | 51.7 | 29 | 38.4 |
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| Population - 2010 | 1,949 | 60,593 | 309,327,143 |
| Population - 2000 | 2,248 | 54,593 | 285,036,114 |
| Population - 1990 | 2,211 | 49,040 | 251,960,433 |
| Pop. 2000 to Now | 2.4% | 17.8% | 15.6% |
| Pop. 1990 to Now | 4.1% | 31.2% | 30.8% |
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| Population Density | 58.5 | 4,922.6 | 93.4 |
| Land Area | 44.5 | 12.7 | 3,531,905.4 |
| Water Area | 0.0 | 3.1 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Three Rivers, CA | Santa Cruz, CA | United States |
| Age 0 to 4 | 1.1% | 3.1% | 5.9% |
| Age 5 to 9 | 4.7% | 3.3% | 6.1% |
| Age 10 to 14 | 8.2% | 3.5% | 6.6% |
| Age 15 to 17 | 3.6% | 2.6% | 3.9% |
| Age 18 to 20 | 0.5% | 17.7% | 4.0% |
| Age 21 to 24 | 1.6% | 13.9% | 5.2% |
| Age 25 to 34 | 7.8% | 12.7% | 13.8% |
| Age 35 to 44 | 7.2% | 10.2% | 12.9% |
| Age 45 to 54 | 20.4% | 10.5% | 12.6% |
| Age 55 to 59 | 12.2% | 5.1% | 6.7% |
| Age 60 to 64 | 7.8% | 5.0% | 6.3% |
| Age 65 to 74 | 17.2% | 8.3% | 9.6% |
| Age 75 to 84 | 6.3% | 2.7% | 4.5% |
| Age 85 and over | 1.5% | 1.4% | 1.9% |
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| Race | | | |
| | Three Rivers, CA | Santa Cruz, CA | United States |
| White | 78.0% | 60.8% | 59.4% |
| Black | 2.1% | 1.8% | 12.2% |
| Asian | 5.3% | 10.6% | 5.6% |
| Native American | 0.9% | 0.1% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.1% | 0.2% |
| Other | 0.0% | 0.5% | 0.4% |
| Two or More Races | 2.9% | 5.1% | 3.2% |
| Hispanic | 10.7% | 21.1% | 18.4% |
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| Marriage & Family | | | |
| | Three Rivers, CA | Santa Cruz, CA | United States |
| Married Population | 56.2% | 31.9% | 49.8% |
| Currently Married | 54.1% | 30.8% | 48.0% |
| Married but Separated | 2.1% | 1.1% | 1.8% |
| Single Population | 43.8% | 68.1% | 50.2% |
| Never Married | 20.8% | 57.2% | 33.8% |
| Divorced | 18.1% | 8.7% | 10.8% |
| Widowed | 5.0% | 2.2% | 5.6% |
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| Household Size | 2.03 | 2.37 | 2.60 |
| Households | 1,278 | 22,067 | 124,010,992 |
| Family Households | 821 | 10,409 | 80,755,759 |
| Married couple, w/children | 16.1% | 29.8% | 30.5% |
| Married couple, no children | 51.4% | 48.8% | 42.9% |
| Non Family Households | 457 | 11,658 | 43,255,233 |
| Single householder, w/children | 26.9% | 13.2% | 15.8% |
| Single householder, no children | 5.6% | 8.2% | 10.8% |