| | Hamilton City, CA | Gridley, CA | United States |
| Population | 2,216 | 7,510 | 329,725,481 |
| Female Population | 50.5% | 50.8% | 50.5% |
| Male Population | 49.5% | 49.2% | 49.5% |
| Median Age | 28.2 | 31.4 | 38.4 |
| space3 | | | |
| Population - 2010 | 1,875 | 6,633 | 309,327,143 |
| Population - 2000 | 1,903 | 5,382 | 285,036,114 |
| Population - 1990 | 1,811 | 4,631 | 251,960,433 |
| Pop. 2000 to Now | 26.4% | 37.4% | 15.6% |
| Pop. 1990 to Now | 32.8% | 59.7% | 30.8% |
| space4 | | | |
| Population Density | 7,102.6 | 3,603.7 | 93.4 |
| Land Area | 0.3 | 2.1 | 3,531,905.4 |
| Water Area | 0.0 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Hamilton City, CA | Gridley, CA | United States |
| Age 0 to 4 | 4.3% | 6.6% | 5.9% |
| Age 5 to 9 | 6.6% | 12.7% | 6.1% |
| Age 10 to 14 | 13.2% | 10.7% | 6.6% |
| Age 15 to 17 | 3.8% | 3.7% | 3.9% |
| Age 18 to 20 | 10.1% | 3.1% | 4.0% |
| Age 21 to 24 | 7.3% | 5.2% | 5.2% |
| Age 25 to 34 | 17.9% | 11.5% | 13.8% |
| Age 35 to 44 | 9.6% | 13.5% | 12.9% |
| Age 45 to 54 | 7.4% | 10.7% | 12.6% |
| Age 55 to 59 | 7.0% | 6.3% | 6.7% |
| Age 60 to 64 | 4.2% | 5.0% | 6.3% |
| Age 65 to 74 | 5.6% | 6.0% | 9.6% |
| Age 75 to 84 | 2.3% | 3.1% | 4.5% |
| Age 85 and over | 0.7% | 1.7% | 1.9% |
| space1 | | | |
| Race | | | |
| | Hamilton City, CA | Gridley, CA | United States |
| White | 3.4% | 56.5% | 59.4% |
| Black | 0.0% | 0.1% | 12.2% |
| Asian | 4.4% | 1.1% | 5.6% |
| Native American | 0.0% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.0% | 0.4% |
| Two or More Races | 0.0% | 4.0% | 3.2% |
| Hispanic | 92.2% | 38.2% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Hamilton City, CA | Gridley, CA | United States |
| Married Population | 48.8% | 57.0% | 49.8% |
| Currently Married | 46.0% | 54.1% | 48.0% |
| Married but Separated | 2.9% | 2.9% | 1.8% |
| Single Population | 51.2% | 43.0% | 50.2% |
| Never Married | 41.6% | 26.9% | 33.8% |
| Divorced | 4.5% | 11.7% | 10.8% |
| Widowed | 5.2% | 4.4% | 5.6% |
| space5 | | | |
| Household Size | 2.92 | 3.01 | 2.60 |
| Households | 758 | 2,460 | 124,010,992 |
| Family Households | 512 | 1,838 | 80,755,759 |
| Married couple, w/children | 38.9% | 36.3% | 30.5% |
| Married couple, no children | 29.1% | 34.3% | 42.9% |
| Non Family Households | 246 | 622 | 43,255,233 |
| Single householder, w/children | 20.7% | 19.0% | 15.8% |
| Single householder, no children | 11.3% | 10.3% | 10.8% |