| | Hiawatha, KS | Clay Center, KS | United States |
| Population | 3,251 | 4,147 | 329,725,481 |
| Female Population | 52.5% | 51.4% | 50.5% |
| Male Population | 47.5% | 48.6% | 49.5% |
| Median Age | 41.5 | 41.3 | 38.4 |
| space3 | | | |
| Population - 2010 | 3,256 | 4,348 | 309,327,143 |
| Population - 2000 | 3,417 | 4,564 | 285,036,114 |
| Population - 1990 | 3,603 | 4,613 | 251,960,433 |
| Pop. 2000 to Now | -9.5% | -12.6% | 15.6% |
| Pop. 1990 to Now | -14.2% | -13.5% | 30.8% |
| space4 | | | |
| Population Density | 1,252.8 | 1,303.3 | 93.4 |
| Land Area | 2.6 | 3.2 | 3,531,905.4 |
| Water Area | 0.0 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Hiawatha, KS | Clay Center, KS | United States |
| Age 0 to 4 | 5.3% | 6.6% | 5.9% |
| Age 5 to 9 | 7.1% | 7.5% | 6.1% |
| Age 10 to 14 | 9.2% | 9.1% | 6.6% |
| Age 15 to 17 | 3.6% | 1.9% | 3.9% |
| Age 18 to 20 | 2.0% | 0.0% | 4.0% |
| Age 21 to 24 | 4.5% | 6.1% | 5.2% |
| Age 25 to 34 | 10.7% | 9.6% | 13.8% |
| Age 35 to 44 | 12.4% | 11.7% | 12.9% |
| Age 45 to 54 | 13.0% | 9.7% | 12.6% |
| Age 55 to 59 | 6.0% | 2.1% | 6.7% |
| Age 60 to 64 | 7.8% | 8.4% | 6.3% |
| Age 65 to 74 | 10.8% | 14.3% | 9.6% |
| Age 75 to 84 | 5.4% | 6.7% | 4.5% |
| Age 85 and over | 2.2% | 6.4% | 1.9% |
| space1 | | | |
| Race | | | |
| | Hiawatha, KS | Clay Center, KS | United States |
| White | 90.0% | 95.4% | 59.4% |
| Black | 1.2% | 3.1% | 12.2% |
| Asian | 0.0% | 0.5% | 5.6% |
| Native American | 1.0% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 1.8% | 0.0% | 0.4% |
| Two or More Races | 3.6% | 0.0% | 3.2% |
| Hispanic | 2.5% | 1.0% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Hiawatha, KS | Clay Center, KS | United States |
| Married Population | 48.0% | 53.2% | 49.8% |
| Currently Married | 47.5% | 52.6% | 48.0% |
| Married but Separated | 0.5% | 0.6% | 1.8% |
| Single Population | 52.0% | 46.8% | 50.2% |
| Never Married | 23.5% | 20.7% | 33.8% |
| Divorced | 20.9% | 11.9% | 10.8% |
| Widowed | 7.6% | 14.1% | 5.6% |
| space5 | | | |
| Household Size | 2.56 | 2.13 | 2.60 |
| Households | 1,247 | 1,903 | 124,010,992 |
| Family Households | 655 | 1,059 | 80,755,759 |
| Married couple, w/children | 31.1% | 30.3% | 30.5% |
| Married couple, no children | 48.1% | 43.7% | 42.9% |
| Non Family Households | 592 | 844 | 43,255,233 |
| Single householder, w/children | 13.3% | 16.6% | 15.8% |
| Single householder, no children | 7.5% | 9.3% | 10.8% |