| | Marquette, KS | Mankato, KS | United States |
| Population | 679 | 954 | 329,725,481 |
| Female Population | 51.8% | 50.0% | 50.5% |
| Male Population | 48.2% | 50.0% | 49.5% |
| Median Age | 52.1 | 47.8 | 38.4 |
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| Population - 2010 | 648 | 866 | 309,327,143 |
| Population - 2000 | 542 | 976 | 285,036,114 |
| Population - 1990 | 593 | 1,037 | 251,960,433 |
| Pop. 2000 to Now | 9.8% | -17.6% | 15.6% |
| Pop. 1990 to Now | 0.3% | -22.5% | 30.8% |
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| Population Density | 1,408.7 | 978.5 | 93.4 |
| Land Area | 0.5 | 1.0 | 3,531,905.4 |
| Water Area | 0.0 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Marquette, KS | Mankato, KS | United States |
| Age 0 to 4 | 4.0% | 5.0% | 5.9% |
| Age 5 to 9 | 5.0% | 7.0% | 6.1% |
| Age 10 to 14 | 4.0% | 8.8% | 6.6% |
| Age 15 to 17 | 2.1% | 6.9% | 3.9% |
| Age 18 to 20 | 2.7% | 0.1% | 4.0% |
| Age 21 to 24 | 5.4% | 2.6% | 5.2% |
| Age 25 to 34 | 5.3% | 6.8% | 13.8% |
| Age 35 to 44 | 11.0% | 9.2% | 12.9% |
| Age 45 to 54 | 15.5% | 10.8% | 12.6% |
| Age 55 to 59 | 6.6% | 9.3% | 6.7% |
| Age 60 to 64 | 4.7% | 8.5% | 6.3% |
| Age 65 to 74 | 27.1% | 11.0% | 9.6% |
| Age 75 to 84 | 4.1% | 7.9% | 4.5% |
| Age 85 and over | 2.5% | 6.0% | 1.9% |
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| Race | | | |
| | Marquette, KS | Mankato, KS | United States |
| White | 92.0% | 91.7% | 59.4% |
| Black | 0.0% | 0.6% | 12.2% |
| Asian | 0.0% | 0.5% | 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 | 1.8% | 1.4% | 3.2% |
| Hispanic | 6.2% | 5.8% | 18.4% |
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| Marriage & Family | | | |
| | Marquette, KS | Mankato, KS | United States |
| Married Population | 54.3% | 54.3% | 49.8% |
| Currently Married | 54.0% | 53.1% | 48.0% |
| Married but Separated | 0.3% | 1.2% | 1.8% |
| Single Population | 45.7% | 45.7% | 50.2% |
| Never Married | 21.7% | 20.8% | 33.8% |
| Divorced | 17.6% | 9.7% | 10.8% |
| Widowed | 6.4% | 15.2% | 5.6% |
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| Household Size | 2.20 | 2.50 | 2.60 |
| Households | 295 | 371 | 124,010,992 |
| Family Households | 181 | 209 | 80,755,759 |
| Married couple, w/children | 15.5% | 29.2% | 30.5% |
| Married couple, no children | 55.2% | 60.8% | 42.9% |
| Non Family Households | 114 | 162 | 43,255,233 |
| Single householder, w/children | 16.6% | 5.3% | 15.8% |
| Single householder, no children | 12.7% | 4.8% | 10.8% |