| | Garden City, ID | Ammon, ID | United States |
| Population | 12,056 | 17,401 | 329,725,481 |
| Female Population | 53.2% | 51.3% | 50.5% |
| Male Population | 46.8% | 48.8% | 49.5% |
| Median Age | 48.4 | 33.1 | 38.4 |
| space3 | | | |
| Population - 2010 | 10,984 | 14,032 | 309,327,143 |
| Population - 2000 | 10,624 | 6,187 | 285,036,114 |
| Population - 1990 | 6,369 | 5,002 | 251,960,433 |
| Pop. 2000 to Now | 12.2% | 186.5% | 15.6% |
| Pop. 1990 to Now | 87.2% | 254.4% | 30.8% |
| space4 | | | |
| Population Density | 2,955.6 | 2,291.4 | 93.4 |
| Land Area | 4.1 | 7.6 | 3,531,905.4 |
| Water Area | 0.2 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Garden City, ID | Ammon, ID | United States |
| Age 0 to 4 | 4.3% | 8.3% | 5.9% |
| Age 5 to 9 | 4.5% | 9.1% | 6.1% |
| Age 10 to 14 | 7.1% | 9.5% | 6.6% |
| Age 15 to 17 | 4.3% | 5.3% | 3.9% |
| Age 18 to 20 | 2.5% | 2.7% | 4.0% |
| Age 21 to 24 | 2.3% | 4.1% | 5.2% |
| Age 25 to 34 | 12.0% | 13.9% | 13.8% |
| Age 35 to 44 | 10.5% | 14.2% | 12.9% |
| Age 45 to 54 | 10.3% | 10.9% | 12.6% |
| Age 55 to 59 | 7.8% | 4.2% | 6.7% |
| Age 60 to 64 | 7.9% | 4.3% | 6.3% |
| Age 65 to 74 | 14.6% | 6.8% | 9.6% |
| Age 75 to 84 | 8.4% | 3.9% | 4.5% |
| Age 85 and over | 3.4% | 2.8% | 1.9% |
| space1 | | | |
| Race | | | |
| | Garden City, ID | Ammon, ID | United States |
| White | 85.1% | 87.8% | 59.4% |
| Black | 0.1% | 0.1% | 12.2% |
| Asian | 1.0% | 0.8% | 5.6% |
| Native American | 0.0% | 0.3% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.3% | 0.4% |
| Two or More Races | 3.3% | 2.1% | 3.2% |
| Hispanic | 10.5% | 8.6% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Garden City, ID | Ammon, ID | United States |
| Married Population | 51.7% | 56.6% | 49.8% |
| Currently Married | 51.0% | 54.8% | 48.0% |
| Married but Separated | 0.7% | 1.8% | 1.8% |
| Single Population | 48.3% | 43.4% | 50.2% |
| Never Married | 25.5% | 24.6% | 33.8% |
| Divorced | 16.3% | 10.3% | 10.8% |
| Widowed | 6.5% | 8.5% | 5.6% |
| space5 | | | |
| Household Size | 2.19 | 2.98 | 2.60 |
| Households | 5,480 | 5,795 | 124,010,992 |
| Family Households | 2,910 | 3,934 | 80,755,759 |
| Married couple, w/children | 20.2% | 42.3% | 30.5% |
| Married couple, no children | 62.5% | 39.3% | 42.9% |
| Non Family Households | 2,570 | 1,861 | 43,255,233 |
| Single householder, w/children | 12.1% | 12.7% | 15.8% |
| Single householder, no children | 5.2% | 5.7% | 10.8% |