| | Glendora, CA | Castaic, CA | United States |
| Population | 52,458 | 18,017 | 329,725,481 |
| Female Population | 52.0% | 50.0% | 50.5% |
| Male Population | 48.0% | 50.0% | 49.5% |
| Median Age | 40 | 38.2 | 38.4 |
| space3 | | | |
| Population - 2010 | 50,258 | 18,134 | 309,327,143 |
| Population - 2000 | 49,415 | 18,001 | 285,036,114 |
| Population - 1990 | 47,828 | 7,647 | 251,960,433 |
| Pop. 2000 to Now | 2.2% | 5.8% | 15.6% |
| Pop. 1990 to Now | 5.6% | 149.0% | 30.8% |
| space4 | | | |
| Population Density | 2,688.9 | 2,481.0 | 93.4 |
| Land Area | 19.5 | 7.3 | 3,531,905.4 |
| Water Area | 0.2 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Glendora, CA | Castaic, CA | United States |
| Age 0 to 4 | 5.3% | 6.5% | 5.9% |
| Age 5 to 9 | 5.7% | 6.5% | 6.1% |
| Age 10 to 14 | 7.3% | 8.1% | 6.6% |
| Age 15 to 17 | 4.6% | 4.5% | 3.9% |
| Age 18 to 20 | 3.3% | 3.0% | 4.0% |
| Age 21 to 24 | 4.5% | 4.2% | 5.2% |
| Age 25 to 34 | 12.7% | 13.4% | 13.8% |
| Age 35 to 44 | 13.5% | 12.5% | 12.9% |
| Age 45 to 54 | 13.3% | 15.2% | 12.6% |
| Age 55 to 59 | 7.9% | 9.2% | 6.7% |
| Age 60 to 64 | 6.3% | 6.1% | 6.3% |
| Age 65 to 74 | 8.9% | 7.5% | 9.6% |
| Age 75 to 84 | 4.6% | 2.5% | 4.5% |
| Age 85 and over | 2.1% | 0.9% | 1.9% |
| space1 | | | |
| Race | | | |
| | Glendora, CA | Castaic, CA | United States |
| White | 43.9% | 49.0% | 59.4% |
| Black | 2.1% | 1.7% | 12.2% |
| Asian | 11.6% | 11.9% | 5.6% |
| Native American | 0.4% | 0.1% | 0.6% |
| Hawaiian, Pacific Islander | 0.2% | 0.1% | 0.2% |
| Other | 0.4% | 1.1% | 0.4% |
| Two or More Races | 3.2% | 7.3% | 3.2% |
| Hispanic | 38.2% | 28.8% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Glendora, CA | Castaic, CA | United States |
| Married Population | 52.9% | 59.6% | 49.8% |
| Currently Married | 52.0% | 58.5% | 48.0% |
| Married but Separated | 1.0% | 1.2% | 1.8% |
| Single Population | 47.1% | 40.4% | 50.2% |
| Never Married | 33.0% | 28.3% | 33.8% |
| Divorced | 9.5% | 7.0% | 10.8% |
| Widowed | 4.6% | 5.1% | 5.6% |
| space5 | | | |
| Household Size | 3.05 | 3.19 | 2.60 |
| Households | 16,861 | 5,656 | 124,010,992 |
| Family Households | 13,036 | 4,727 | 80,755,759 |
| Married couple, w/children | 35.0% | 41.3% | 30.5% |
| Married couple, no children | 41.1% | 41.1% | 42.9% |
| Non Family Households | 3,825 | 929 | 43,255,233 |
| Single householder, w/children | 11.7% | 6.5% | 15.8% |
| Single householder, no children | 12.2% | 11.1% | 10.8% |