| | American Canyon, CA | St. Helena, CA | United States |
| Population | 21,735 | 5,530 | 329,725,481 |
| Female Population | 50.5% | 50.6% | 50.5% |
| Male Population | 49.5% | 49.4% | 49.5% |
| Median Age | 36.8 | 47.9 | 38.4 |
| space3 | | | |
| Population - 2010 | 19,617 | 5,819 | 309,327,143 |
| Population - 2000 | 9,774 | 5,950 | 285,036,114 |
| Population - 1990 | 7,706 | 4,990 | 251,960,433 |
| Pop. 2000 to Now | 104.2% | 0.2% | 15.6% |
| Pop. 1990 to Now | 159.0% | 19.4% | 30.8% |
| space4 | | | |
| Population Density | 3,571.3 | 1,116.0 | 93.4 |
| Land Area | 6.1 | 5.0 | 3,531,905.4 |
| Water Area | 0.0 | 0.1 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | American Canyon, CA | St. Helena, CA | United States |
| Age 0 to 4 | 4.8% | 5.7% | 5.9% |
| Age 5 to 9 | 6.0% | 4.4% | 6.1% |
| Age 10 to 14 | 9.0% | 2.5% | 6.6% |
| Age 15 to 17 | 5.3% | 3.5% | 3.9% |
| Age 18 to 20 | 4.7% | 4.3% | 4.0% |
| Age 21 to 24 | 6.1% | 2.2% | 5.2% |
| Age 25 to 34 | 12.1% | 9.5% | 13.8% |
| Age 35 to 44 | 12.8% | 15.0% | 12.9% |
| Age 45 to 54 | 15.4% | 11.2% | 12.6% |
| Age 55 to 59 | 6.4% | 7.4% | 6.7% |
| Age 60 to 64 | 5.8% | 4.6% | 6.3% |
| Age 65 to 74 | 7.2% | 16.7% | 9.6% |
| Age 75 to 84 | 3.4% | 9.5% | 4.5% |
| Age 85 and over | 1.2% | 3.6% | 1.9% |
| space1 | | | |
| Race | | | |
| | American Canyon, CA | St. Helena, CA | United States |
| White | 19.5% | 71.3% | 59.4% |
| Black | 7.5% | 0.7% | 12.2% |
| Asian | 33.3% | 2.0% | 5.6% |
| Native American | 0.6% | 0.2% | 0.6% |
| Hawaiian, Pacific Islander | 0.8% | 0.0% | 0.2% |
| Other | 0.5% | 0.0% | 0.4% |
| Two or More Races | 7.3% | 2.3% | 3.2% |
| Hispanic | 30.6% | 23.6% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | American Canyon, CA | St. Helena, CA | United States |
| Married Population | 51.3% | 55.0% | 49.8% |
| Currently Married | 50.1% | 53.0% | 48.0% |
| Married but Separated | 1.2% | 2.0% | 1.8% |
| Single Population | 48.7% | 45.0% | 50.2% |
| Never Married | 35.7% | 27.1% | 33.8% |
| Divorced | 8.2% | 12.0% | 10.8% |
| Widowed | 4.8% | 5.9% | 5.6% |
| space5 | | | |
| Household Size | 3.91 | 2.21 | 2.60 |
| Households | 5,540 | 2,466 | 124,010,992 |
| Family Households | 4,753 | 1,555 | 80,755,759 |
| Married couple, w/children | 44.4% | 31.0% | 30.5% |
| Married couple, no children | 31.1% | 47.1% | 42.9% |
| Non Family Households | 787 | 911 | 43,255,233 |
| Single householder, w/children | 12.1% | 10.9% | 15.8% |
| Single householder, no children | 12.5% | 11.0% | 10.8% |