| | Willits, CA | Fontana, CA | United States |
| Population | 5,008 | 208,087 | 329,725,481 |
| Female Population | 54.1% | 49.7% | 50.5% |
| Male Population | 45.9% | 50.3% | 49.5% |
| Median Age | 41.7 | 32 | 38.4 |
| space3 | | | |
| Population - 2010 | 4,922 | 197,216 | 309,327,143 |
| Population - 2000 | 5,073 | 128,929 | 285,036,114 |
| Population - 1990 | 5,027 | 87,535 | 251,960,433 |
| Pop. 2000 to Now | -4.8% | 67.7% | 15.6% |
| Pop. 1990 to Now | -3.9% | 147.0% | 30.8% |
| space4 | | | |
| Population Density | 1,777.8 | 4,830.7 | 93.4 |
| Land Area | 2.8 | 43.1 | 3,531,905.4 |
| Water Area | 0.0 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Willits, CA | Fontana, CA | United States |
| Age 0 to 4 | 4.5% | 6.5% | 5.9% |
| Age 5 to 9 | 5.6% | 7.8% | 6.1% |
| Age 10 to 14 | 7.4% | 8.9% | 6.6% |
| Age 15 to 17 | 1.7% | 5.6% | 3.9% |
| Age 18 to 20 | 3.4% | 5.1% | 4.0% |
| Age 21 to 24 | 5.0% | 6.0% | 5.2% |
| Age 25 to 34 | 12.8% | 14.3% | 13.8% |
| Age 35 to 44 | 12.7% | 15.0% | 12.9% |
| Age 45 to 54 | 9.2% | 13.3% | 12.6% |
| Age 55 to 59 | 3.8% | 5.1% | 6.7% |
| Age 60 to 64 | 3.8% | 4.0% | 6.3% |
| Age 65 to 74 | 16.7% | 5.4% | 9.6% |
| Age 75 to 84 | 9.5% | 2.2% | 4.5% |
| Age 85 and over | 4.1% | 0.7% | 1.9% |
| space1 | | | |
| Race | | | |
| | Willits, CA | Fontana, CA | United States |
| White | 68.7% | 13.4% | 59.4% |
| Black | 1.0% | 8.4% | 12.2% |
| Asian | 0.2% | 6.6% | 5.6% |
| Native American | 1.5% | 0.3% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.1% | 0.2% |
| Other | 0.0% | 0.3% | 0.4% |
| Two or More Races | 4.1% | 2.8% | 3.2% |
| Hispanic | 24.5% | 68.2% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Willits, CA | Fontana, CA | United States |
| Married Population | 32.1% | 49.0% | 49.8% |
| Currently Married | 29.1% | 47.1% | 48.0% |
| Married but Separated | 3.1% | 1.9% | 1.8% |
| Single Population | 67.9% | 51.0% | 50.2% |
| Never Married | 33.7% | 39.4% | 33.8% |
| Divorced | 22.2% | 7.7% | 10.8% |
| Widowed | 12.0% | 3.8% | 5.6% |
| space5 | | | |
| Household Size | 2.13 | 3.75 | 2.60 |
| Households | 2,311 | 55,307 | 124,010,992 |
| Family Households | 982 | 47,517 | 80,755,759 |
| Married couple, w/children | 22.4% | 42.4% | 30.5% |
| Married couple, no children | 29.6% | 26.3% | 42.9% |
| Non Family Households | 1,329 | 7,790 | 43,255,233 |
| Single householder, w/children | 28.3% | 18.1% | 15.8% |
| Single householder, no children | 19.7% | 13.2% | 10.8% |