| | Middletown, CA | Lower Lake, CA | United States |
| Population | 1,577 | 1,036 | 329,725,481 |
| Female Population | 51.7% | 57.6% | 50.5% |
| Male Population | 48.3% | 42.4% | 49.5% |
| Median Age | 33.1 | 53.3 | 38.4 |
| space3 | | | |
| Population - 2010 | 1,646 | 1,247 | 309,327,143 |
| Population - 2000 | 1,020 | 1,755 | 285,036,114 |
| Population - 1990 | 867 | 1,217 | 251,960,433 |
| Pop. 2000 to Now | -38.3% | -17.5% | 15.6% |
| Pop. 1990 to Now | -27.5% | 19.0% | 30.8% |
| space4 | | | |
| Population Density | 855.2 | 388.5 | 93.4 |
| Land Area | 1.8 | 2.7 | 3,531,905.4 |
| Water Area | 0.0 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Middletown, CA | Lower Lake, CA | United States |
| Age 0 to 4 | 6.0% | 4.1% | 5.9% |
| Age 5 to 9 | 1.6% | 10.1% | 6.1% |
| Age 10 to 14 | 16.0% | 7.0% | 6.6% |
| Age 15 to 17 | 8.8% | 5.7% | 3.9% |
| Age 18 to 20 | 3.2% | 4.5% | 4.0% |
| Age 21 to 24 | 3.9% | 0.1% | 5.2% |
| Age 25 to 34 | 11.7% | 7.5% | 13.8% |
| Age 35 to 44 | 5.8% | 5.6% | 12.9% |
| Age 45 to 54 | 20.2% | 9.6% | 12.6% |
| Age 55 to 59 | 2.9% | 7.2% | 6.7% |
| Age 60 to 64 | 10.6% | 9.5% | 6.3% |
| Age 65 to 74 | 9.4% | 11.8% | 9.6% |
| Age 75 to 84 | 0.0% | 16.4% | 4.5% |
| Age 85 and over | 0.0% | 1.0% | 1.9% |
| space1 | | | |
| Race | | | |
| | Middletown, CA | Lower Lake, CA | United States |
| White | 60.4% | 48.4% | 59.4% |
| Black | 0.0% | 0.1% | 12.2% |
| Asian | 0.0% | 0.7% | 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% | 1.4% | 3.2% |
| Hispanic | 39.6% | 49.4% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Middletown, CA | Lower Lake, CA | United States |
| Married Population | 49.1% | 66.8% | 49.8% |
| Currently Married | 48.1% | 58.9% | 48.0% |
| Married but Separated | 1.0% | 8.0% | 1.8% |
| Single Population | 50.9% | 33.2% | 50.2% |
| Never Married | 32.4% | 19.3% | 33.8% |
| Divorced | 12.3% | 4.7% | 10.8% |
| Widowed | 6.2% | 9.2% | 5.6% |
| space5 | | | |
| Household Size | 3.09 | 2.57 | 2.60 |
| Households | 510 | 401 | 124,010,992 |
| Family Households | 399 | 267 | 80,755,759 |
| Married couple, w/children | 35.1% | 33.0% | 30.5% |
| Married couple, no children | 29.3% | 50.9% | 42.9% |
| Non Family Households | 111 | 134 | 43,255,233 |
| Single householder, w/children | 32.3% | 9.7% | 15.8% |
| Single householder, no children | 3.3% | 6.4% | 10.8% |