| | Garnett, KS | Kansas City, KS | United States |
| Population | 3,219 | 155,745 | 329,725,481 |
| Female Population | 51.9% | 49.7% | 50.5% |
| Male Population | 48.1% | 50.3% | 49.5% |
| Median Age | 42.3 | 33.8 | 38.4 |
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| Population - 2010 | 3,413 | 145,881 | 309,327,143 |
| Population - 2000 | 3,368 | 146,866 | 285,036,114 |
| Population - 1990 | 3,210 | 149,767 | 251,960,433 |
| Pop. 2000 to Now | -3.3% | 4.0% | 15.6% |
| Pop. 1990 to Now | 1.5% | 2.0% | 30.8% |
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| Population Density | 1,044.5 | 1,247.8 | 93.4 |
| Land Area | 3.1 | 124.8 | 3,531,905.4 |
| Water Area | 0.1 | 3.6 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Garnett, KS | Kansas City, KS | United States |
| Age 0 to 4 | 6.4% | 7.7% | 5.9% |
| Age 5 to 9 | 6.4% | 7.6% | 6.1% |
| Age 10 to 14 | 7.1% | 8.2% | 6.6% |
| Age 15 to 17 | 3.1% | 4.3% | 3.9% |
| Age 18 to 20 | 2.2% | 3.9% | 4.0% |
| Age 21 to 24 | 4.7% | 5.0% | 5.2% |
| Age 25 to 34 | 10.0% | 14.9% | 13.8% |
| Age 35 to 44 | 13.3% | 13.3% | 12.9% |
| Age 45 to 54 | 10.4% | 11.1% | 12.6% |
| Age 55 to 59 | 6.0% | 5.8% | 6.7% |
| Age 60 to 64 | 8.2% | 5.8% | 6.3% |
| Age 65 to 74 | 8.3% | 7.7% | 9.6% |
| Age 75 to 84 | 9.3% | 3.5% | 4.5% |
| Age 85 and over | 4.4% | 1.1% | 1.9% |
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| Race | | | |
| | Garnett, KS | Kansas City, KS | United States |
| White | 88.9% | 37.1% | 59.4% |
| Black | 1.0% | 21.4% | 12.2% |
| Asian | 0.0% | 5.4% | 5.6% |
| Native American | 1.2% | 0.3% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.2% | 0.2% |
| Other | 0.0% | 0.4% | 0.4% |
| Two or More Races | 4.7% | 4.0% | 3.2% |
| Hispanic | 4.2% | 31.2% | 18.4% |
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| Marriage & Family | | | |
| | Garnett, KS | Kansas City, KS | United States |
| Married Population | 52.0% | 44.5% | 49.8% |
| Currently Married | 50.8% | 42.1% | 48.0% |
| Married but Separated | 1.2% | 2.4% | 1.8% |
| Single Population | 48.0% | 55.5% | 50.2% |
| Never Married | 23.3% | 38.6% | 33.8% |
| Divorced | 14.9% | 12.1% | 10.8% |
| Widowed | 9.8% | 4.8% | 5.6% |
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| Household Size | 2.25 | 2.75 | 2.60 |
| Households | 1,383 | 56,289 | 124,010,992 |
| Family Households | 806 | 35,376 | 80,755,759 |
| Married couple, w/children | 23.7% | 31.0% | 30.5% |
| Married couple, no children | 48.9% | 33.5% | 42.9% |
| Non Family Households | 577 | 20,913 | 43,255,233 |
| Single householder, w/children | 20.2% | 22.2% | 15.8% |
| Single householder, no children | 7.2% | 13.2% | 10.8% |