| | Fortuna, CA | Walnut Creek, CA | United States |
| Population | 12,480 | 69,876 | 329,725,481 |
| Female Population | 52.4% | 52.4% | 50.5% |
| Male Population | 47.6% | 47.6% | 49.5% |
| Median Age | 40.2 | 47.8 | 38.4 |
| space3 | | | |
| Population - 2010 | 12,030 | 64,376 | 309,327,143 |
| Population - 2000 | 10,497 | 64,296 | 285,036,114 |
| Population - 1990 | 8,788 | 60,569 | 251,960,433 |
| Pop. 2000 to Now | 15.3% | 8.8% | 15.6% |
| Pop. 1990 to Now | 37.8% | 15.5% | 30.8% |
| space4 | | | |
| Population Density | 2,444.7 | 3,537.0 | 93.4 |
| Land Area | 5.1 | 19.8 | 3,531,905.4 |
| Water Area | 0.0 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Fortuna, CA | Walnut Creek, CA | United States |
| Age 0 to 4 | 5.6% | 4.8% | 5.9% |
| Age 5 to 9 | 7.3% | 4.5% | 6.1% |
| Age 10 to 14 | 4.8% | 3.8% | 6.6% |
| Age 15 to 17 | 5.1% | 2.9% | 3.9% |
| Age 18 to 20 | 4.7% | 2.0% | 4.0% |
| Age 21 to 24 | 4.8% | 3.2% | 5.2% |
| Age 25 to 34 | 12.6% | 13.8% | 13.8% |
| Age 35 to 44 | 11.0% | 12.2% | 12.9% |
| Age 45 to 54 | 12.6% | 10.5% | 12.6% |
| Age 55 to 59 | 8.7% | 6.8% | 6.7% |
| Age 60 to 64 | 7.0% | 5.9% | 6.3% |
| Age 65 to 74 | 8.0% | 14.2% | 9.6% |
| Age 75 to 84 | 4.3% | 9.5% | 4.5% |
| Age 85 and over | 3.6% | 5.8% | 1.9% |
| space1 | | | |
| Race | | | |
| | Fortuna, CA | Walnut Creek, CA | United States |
| White | 68.4% | 63.4% | 59.4% |
| Black | 0.7% | 2.3% | 12.2% |
| Asian | 1.5% | 17.7% | 5.6% |
| Native American | 1.5% | 0.1% | 0.6% |
| Hawaiian, Pacific Islander | 0.3% | 0.4% | 0.2% |
| Other | 0.2% | 0.1% | 0.4% |
| Two or More Races | 4.2% | 6.0% | 3.2% |
| Hispanic | 23.3% | 10.1% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Fortuna, CA | Walnut Creek, CA | United States |
| Married Population | 45.9% | 55.5% | 49.8% |
| Currently Married | 44.0% | 54.2% | 48.0% |
| Married but Separated | 1.9% | 1.3% | 1.8% |
| Single Population | 54.1% | 44.5% | 50.2% |
| Never Married | 32.2% | 25.6% | 33.8% |
| Divorced | 14.2% | 10.5% | 10.8% |
| Widowed | 7.7% | 8.4% | 5.6% |
| space5 | | | |
| Household Size | 2.52 | 2.15 | 2.60 |
| Households | 4,901 | 32,126 | 124,010,992 |
| Family Households | 3,136 | 18,388 | 80,755,759 |
| Married couple, w/children | 26.6% | 29.4% | 30.5% |
| Married couple, no children | 40.6% | 55.3% | 42.9% |
| Non Family Households | 1,765 | 13,738 | 43,255,233 |
| Single householder, w/children | 22.5% | 7.8% | 15.8% |
| Single householder, no children | 10.3% | 7.5% | 10.8% |