| | St. Johns, AZ | Maricopa, AZ | United States |
| Population | 3,416 | 57,075 | 329,725,481 |
| Female Population | 43.1% | 51.3% | 50.5% |
| Male Population | 56.9% | 48.7% | 49.5% |
| Median Age | 26.9 | 36.3 | 38.4 |
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| Population - 2010 | 3,494 | 43,692 | 309,327,143 |
| Population - 2000 | 3,269 | 1,040 | 285,036,114 |
| Population - 1990 | 3,294 | 1,085 | 251,960,433 |
| Pop. 2000 to Now | 7.9% | 5,144.1% | 15.6% |
| Pop. 1990 to Now | 7.0% | 4,926.6% | 30.8% |
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| Population Density | 131.9 | 1,333.6 | 93.4 |
| Land Area | 25.9 | 42.8 | 3,531,905.4 |
| Water Area | 0.2 | 0.1 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | St. Johns, AZ | Maricopa, AZ | United States |
| Age 0 to 4 | 6.1% | 6.6% | 5.9% |
| Age 5 to 9 | 8.5% | 7.9% | 6.1% |
| Age 10 to 14 | 11.8% | 9.2% | 6.6% |
| Age 15 to 17 | 5.4% | 4.6% | 3.9% |
| Age 18 to 20 | 11.4% | 2.9% | 4.0% |
| Age 21 to 24 | 5.2% | 3.9% | 5.2% |
| Age 25 to 34 | 9.0% | 12.9% | 13.8% |
| Age 35 to 44 | 9.2% | 15.6% | 12.9% |
| Age 45 to 54 | 12.0% | 12.9% | 12.6% |
| Age 55 to 59 | 0.8% | 4.5% | 6.7% |
| Age 60 to 64 | 10.6% | 4.7% | 6.3% |
| Age 65 to 74 | 8.3% | 10.4% | 9.6% |
| Age 75 to 84 | 1.5% | 3.5% | 4.5% |
| Age 85 and over | 0.1% | 0.5% | 1.9% |
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| Race | | | |
| | St. Johns, AZ | Maricopa, AZ | United States |
| White | 44.9% | 46.6% | 59.4% |
| Black | 5.4% | 12.1% | 12.2% |
| Asian | 0.0% | 3.1% | 5.6% |
| Native American | 8.6% | 1.1% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 1.1% | 0.2% |
| Other | 0.3% | 0.7% | 0.4% |
| Two or More Races | 1.2% | 4.5% | 3.2% |
| Hispanic | 39.5% | 30.8% | 18.4% |
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| Marriage & Family | | | |
| | St. Johns, AZ | Maricopa, AZ | United States |
| Married Population | 47.7% | 58.1% | 49.8% |
| Currently Married | 45.9% | 57.2% | 48.0% |
| Married but Separated | 1.8% | 1.0% | 1.8% |
| Single Population | 52.3% | 41.9% | 50.2% |
| Never Married | 35.9% | 28.7% | 33.8% |
| Divorced | 14.9% | 9.7% | 10.8% |
| Widowed | 1.6% | 3.5% | 5.6% |
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| Household Size | 3.93 | 3.12 | 2.60 |
| Households | 841 | 18,282 | 124,010,992 |
| Family Households | 644 | 14,694 | 80,755,759 |
| Married couple, w/children | 33.5% | 35.2% | 30.5% |
| Married couple, no children | 31.2% | 43.5% | 42.9% |
| Non Family Households | 197 | 3,588 | 43,255,233 |
| Single householder, w/children | 18.6% | 15.5% | 15.8% |
| Single householder, no children | 16.6% | 5.9% | 10.8% |