| | Quincy, CA | Colusa, CA | United States |
| Population | 1,786 | 6,359 | 329,725,481 |
| Female Population | 58.2% | 49.6% | 50.5% |
| Male Population | 41.8% | 50.4% | 49.5% |
| Median Age | 41.8 | 37.7 | 38.4 |
| space3 | | | |
| Population - 2010 | 1,529 | 6,226 | 309,327,143 |
| Population - 2000 | 1,879 | 5,402 | 285,036,114 |
| Population - 1990 | 1,820 | 4,934 | 251,960,433 |
| Pop. 2000 to Now | 6.0% | 12.9% | 15.6% |
| Pop. 1990 to Now | 9.5% | 23.6% | 30.8% |
| space4 | | | |
| Population Density | 422.8 | 3,467.3 | 93.4 |
| Land Area | 4.2 | 1.8 | 3,531,905.4 |
| Water Area | 0.0 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Quincy, CA | Colusa, CA | United States |
| Age 0 to 4 | 2.2% | 6.3% | 5.9% |
| Age 5 to 9 | 2.8% | 8.9% | 6.1% |
| Age 10 to 14 | 5.2% | 6.6% | 6.6% |
| Age 15 to 17 | 7.8% | 5.9% | 3.9% |
| Age 18 to 20 | 12.9% | 2.0% | 4.0% |
| Age 21 to 24 | 0.8% | 3.8% | 5.2% |
| Age 25 to 34 | 10.5% | 13.2% | 13.8% |
| Age 35 to 44 | 12.6% | 14.4% | 12.9% |
| Age 45 to 54 | 7.2% | 10.9% | 12.6% |
| Age 55 to 59 | 11.4% | 6.3% | 6.7% |
| Age 60 to 64 | 7.7% | 5.9% | 6.3% |
| Age 65 to 74 | 11.9% | 9.4% | 9.6% |
| Age 75 to 84 | 5.4% | 4.2% | 4.5% |
| Age 85 and over | 1.6% | 2.3% | 1.9% |
| space1 | | | |
| Race | | | |
| | Quincy, CA | Colusa, CA | United States |
| White | 78.3% | 34.4% | 59.4% |
| Black | 10.8% | 2.9% | 12.2% |
| Asian | 0.0% | 0.8% | 5.6% |
| Native American | 1.7% | 0.6% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.0% | 0.4% |
| Two or More Races | 3.7% | 3.2% | 3.2% |
| Hispanic | 5.6% | 58.1% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Quincy, CA | Colusa, CA | United States |
| Married Population | 38.7% | 49.4% | 49.8% |
| Currently Married | 38.7% | 46.7% | 48.0% |
| Married but Separated | 0.0% | 2.7% | 1.8% |
| Single Population | 61.3% | 50.6% | 50.2% |
| Never Married | 46.0% | 31.6% | 33.8% |
| Divorced | 11.5% | 11.9% | 10.8% |
| Widowed | 3.7% | 7.1% | 5.6% |
| space5 | | | |
| Household Size | 2.47 | 2.59 | 2.60 |
| Households | 701 | 2,431 | 124,010,992 |
| Family Households | 386 | 1,565 | 80,755,759 |
| Married couple, w/children | 29.8% | 30.5% | 30.5% |
| Married couple, no children | 46.4% | 36.4% | 42.9% |
| Non Family Households | 315 | 866 | 43,255,233 |
| Single householder, w/children | 22.0% | 24.1% | 15.8% |
| Single householder, no children | 1.8% | 9.0% | 10.8% |