| | Hays, KS | Castle Rock, CO | United States |
| Population | 20,870 | 71,037 | 329,725,481 |
| Female Population | 50.5% | 50.4% | 50.5% |
| Male Population | 49.5% | 49.6% | 49.5% |
| Median Age | 32.5 | 35.7 | 38.4 |
| space3 | | | |
| Population - 2010 | 20,517 | 48,793 | 309,327,143 |
| Population - 2000 | 20,013 | 20,224 | 285,036,114 |
| Population - 1990 | 17,767 | 8,708 | 251,960,433 |
| Pop. 2000 to Now | 4.1% | 248.9% | 15.6% |
| Pop. 1990 to Now | 17.2% | 710.4% | 30.8% |
| space4 | | | |
| Population Density | 2,488.7 | 2,073.2 | 93.4 |
| Land Area | 8.4 | 34.3 | 3,531,905.4 |
| Water Area | 0.0 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Hays, KS | Castle Rock, CO | United States |
| Age 0 to 4 | 4.9% | 7.4% | 5.9% |
| Age 5 to 9 | 6.1% | 8.2% | 6.1% |
| Age 10 to 14 | 6.2% | 7.2% | 6.6% |
| Age 15 to 17 | 2.7% | 5.3% | 3.9% |
| Age 18 to 20 | 8.8% | 4.1% | 4.0% |
| Age 21 to 24 | 11.3% | 3.6% | 5.2% |
| Age 25 to 34 | 13.4% | 12.9% | 13.8% |
| Age 35 to 44 | 11.6% | 16.2% | 12.9% |
| Age 45 to 54 | 8.7% | 14.3% | 12.6% |
| Age 55 to 59 | 4.0% | 6.1% | 6.7% |
| Age 60 to 64 | 6.3% | 4.7% | 6.3% |
| Age 65 to 74 | 8.6% | 6.1% | 9.6% |
| Age 75 to 84 | 4.3% | 3.0% | 4.5% |
| Age 85 and over | 3.1% | 1.0% | 1.9% |
| space1 | | | |
| Race | | | |
| | Hays, KS | Castle Rock, CO | United States |
| White | 88.5% | 81.6% | 59.4% |
| Black | 0.8% | 0.5% | 12.2% |
| Asian | 2.3% | 2.0% | 5.6% |
| Native American | 0.2% | 0.3% | 0.6% |
| Hawaiian, Pacific Islander | 0.1% | 0.2% | 0.2% |
| Other | 0.1% | 0.6% | 0.4% |
| Two or More Races | 1.9% | 3.8% | 3.2% |
| Hispanic | 6.1% | 11.0% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Hays, KS | Castle Rock, CO | United States |
| Married Population | 46.0% | 62.5% | 49.8% |
| Currently Married | 45.3% | 61.8% | 48.0% |
| Married but Separated | 0.7% | 0.7% | 1.8% |
| Single Population | 54.0% | 37.5% | 50.2% |
| Never Married | 39.2% | 24.5% | 33.8% |
| Divorced | 8.1% | 10.0% | 10.8% |
| Widowed | 6.7% | 3.0% | 5.6% |
| space5 | | | |
| Household Size | 2.30 | 2.83 | 2.60 |
| Households | 8,613 | 24,867 | 124,010,992 |
| Family Households | 4,703 | 19,112 | 80,755,759 |
| Married couple, w/children | 35.8% | 48.9% | 30.5% |
| Married couple, no children | 44.4% | 37.4% | 42.9% |
| Non Family Households | 3,910 | 5,755 | 43,255,233 |
| Single householder, w/children | 13.3% | 8.6% | 15.8% |
| Single householder, no children | 6.4% | 5.1% | 10.8% |