| | Mill Valley, CA | Manhattan Beach, CA | United States |
| Population | 14,240 | 35,585 | 329,725,481 |
| Female Population | 52.5% | 50.7% | 50.5% |
| Male Population | 47.5% | 49.3% | 49.5% |
| Median Age | 47.9 | 42.8 | 38.4 |
| space3 | | | |
| Population - 2010 | 13,934 | 35,149 | 309,327,143 |
| Population - 2000 | 13,600 | 33,852 | 285,036,114 |
| Population - 1990 | 13,038 | 32,063 | 251,960,433 |
| Pop. 2000 to Now | 5.3% | 1.3% | 15.6% |
| Pop. 1990 to Now | 9.9% | 7.0% | 30.8% |
| space4 | | | |
| Population Density | 2,989.7 | 9,038.6 | 93.4 |
| Land Area | 4.8 | 3.9 | 3,531,905.4 |
| Water Area | 0.1 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Mill Valley, CA | Manhattan Beach, CA | United States |
| Age 0 to 4 | 2.9% | 4.9% | 5.9% |
| Age 5 to 9 | 5.8% | 8.4% | 6.1% |
| Age 10 to 14 | 6.3% | 8.6% | 6.6% |
| Age 15 to 17 | 6.1% | 5.7% | 3.9% |
| Age 18 to 20 | 3.4% | 1.8% | 4.0% |
| Age 21 to 24 | 1.5% | 2.0% | 5.2% |
| Age 25 to 34 | 7.3% | 8.2% | 13.8% |
| Age 35 to 44 | 12.2% | 13.9% | 12.9% |
| Age 45 to 54 | 18.4% | 16.3% | 12.6% |
| Age 55 to 59 | 7.8% | 7.3% | 6.7% |
| Age 60 to 64 | 7.1% | 7.3% | 6.3% |
| Age 65 to 74 | 11.6% | 9.0% | 9.6% |
| Age 75 to 84 | 6.5% | 4.8% | 4.5% |
| Age 85 and over | 3.0% | 1.8% | 1.9% |
| space1 | | | |
| Race | | | |
| | Mill Valley, CA | Manhattan Beach, CA | United States |
| White | 83.0% | 71.3% | 59.4% |
| Black | 1.4% | 0.5% | 12.2% |
| Asian | 6.1% | 14.7% | 5.6% |
| Native American | 0.0% | 0.1% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.1% | 0.2% |
| Other | 1.0% | 0.3% | 0.4% |
| Two or More Races | 5.4% | 5.5% | 3.2% |
| Hispanic | 3.0% | 7.6% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Mill Valley, CA | Manhattan Beach, CA | United States |
| Married Population | 56.1% | 59.8% | 49.8% |
| Currently Married | 55.6% | 58.9% | 48.0% |
| Married but Separated | 0.5% | 1.0% | 1.8% |
| Single Population | 43.9% | 40.2% | 50.2% |
| Never Married | 26.9% | 26.5% | 33.8% |
| Divorced | 12.5% | 9.2% | 10.8% |
| Widowed | 4.5% | 4.5% | 5.6% |
| space5 | | | |
| Household Size | 2.52 | 2.65 | 2.60 |
| Households | 5,622 | 13,422 | 124,010,992 |
| Family Households | 3,814 | 9,317 | 80,755,759 |
| Married couple, w/children | 35.2% | 44.6% | 30.5% |
| Married couple, no children | 49.5% | 40.3% | 42.9% |
| Non Family Households | 1,808 | 4,105 | 43,255,233 |
| Single householder, w/children | 9.8% | 8.2% | 15.8% |
| Single householder, no children | 5.6% | 6.9% | 10.8% |