| | Fort Riley, KS | Altus, OK | United States |
| Population | 8,006 | 18,825 | 329,725,481 |
| Female Population | 35.7% | 50.1% | 50.5% |
| Male Population | 64.3% | 49.9% | 49.5% |
| Median Age | 22.6 | 33.2 | 38.4 |
| space3 | | | |
| Population - 2010 | 8,423 | 19,786 | 309,327,143 |
| Population - 2000 | 6,958 | 21,447 | 285,036,114 |
| Population - 1990 | 12,050 | 21,910 | 251,960,433 |
| Pop. 2000 to Now | 6.3% | -15.3% | 15.6% |
| Pop. 1990 to Now | -38.6% | -17.1% | 30.8% |
| space4 | | | |
| Population Density | 1,568.0 | 1,024.8 | 93.4 |
| Land Area | 5.1 | 18.4 | 3,531,905.4 |
| Water Area | 0.0 | 0.2 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Fort Riley, KS | Altus, OK | United States |
| Age 0 to 4 | 14.0% | 7.4% | 5.9% |
| Age 5 to 9 | 4.7% | 8.4% | 6.1% |
| Age 10 to 14 | 2.8% | 5.9% | 6.6% |
| Age 15 to 17 | 0.8% | 3.8% | 3.9% |
| Age 18 to 20 | 12.4% | 4.2% | 4.0% |
| Age 21 to 24 | 31.9% | 6.7% | 5.2% |
| Age 25 to 34 | 25.5% | 16.2% | 13.8% |
| Age 35 to 44 | 6.8% | 12.3% | 12.9% |
| Age 45 to 54 | 0.5% | 10.6% | 12.6% |
| Age 55 to 59 | 0.2% | 6.7% | 6.7% |
| Age 60 to 64 | 0.4% | 4.7% | 6.3% |
| Age 65 to 74 | 0.0% | 6.9% | 9.6% |
| Age 75 to 84 | 0.0% | 3.9% | 4.5% |
| Age 85 and over | 0.0% | 2.2% | 1.9% |
| space1 | | | |
| Race | | | |
| | Fort Riley, KS | Altus, OK | United States |
| White | 56.5% | 57.5% | 59.4% |
| Black | 16.1% | 8.0% | 12.2% |
| Asian | 2.0% | 1.9% | 5.6% |
| Native American | 0.1% | 1.1% | 0.6% |
| Hawaiian, Pacific Islander | 0.1% | 0.2% | 0.2% |
| Other | 0.0% | 0.1% | 0.4% |
| Two or More Races | 4.3% | 3.6% | 3.2% |
| Hispanic | 21.0% | 27.7% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Fort Riley, KS | Altus, OK | United States |
| Married Population | 53.5% | 53.1% | 49.8% |
| Currently Married | 52.3% | 49.6% | 48.0% |
| Married but Separated | 1.2% | 3.5% | 1.8% |
| Single Population | 46.5% | 46.9% | 50.2% |
| Never Married | 45.5% | 29.9% | 33.8% |
| Divorced | 0.7% | 10.0% | 10.8% |
| Widowed | 0.3% | 7.0% | 5.6% |
| space5 | | | |
| Household Size | 2.77 | 2.52 | 2.60 |
| Households | 1,911 | 7,248 | 124,010,992 |
| Family Households | 1,637 | 4,549 | 80,755,759 |
| Married couple, w/children | 55.3% | 36.9% | 30.5% |
| Married couple, no children | 35.9% | 38.4% | 42.9% |
| Non Family Households | 274 | 2,699 | 43,255,233 |
| Single householder, w/children | 8.8% | 17.5% | 15.8% |
| Single householder, no children | 0.0% | 7.2% | 10.8% |