| | Oak Park, IL | Fort Collins, CO | United States |
| Population | 54,100 | 166,788 | 329,725,481 |
| Female Population | 53.0% | 49.4% | 50.5% |
| Male Population | 47.0% | 50.6% | 49.5% |
| Median Age | 39.9 | 30 | 38.4 |
| space3 | | | |
| Population - 2010 | 51,896 | 145,123 | 309,327,143 |
| Population - 2000 | 52,524 | 118,652 | 285,036,114 |
| Population - 1990 | 53,648 | 87,758 | 251,960,433 |
| Pop. 2000 to Now | -1.3% | 41.8% | 15.6% |
| Pop. 1990 to Now | -3.4% | 91.7% | 30.8% |
| space4 | | | |
| Population Density | 11,510.6 | 2,941.6 | 93.4 |
| Land Area | 4.7 | 56.7 | 3,531,905.4 |
| Water Area | 0.0 | 1.3 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Oak Park, IL | Fort Collins, CO | United States |
| Age 0 to 4 | 5.3% | 4.1% | 5.9% |
| Age 5 to 9 | 7.3% | 5.0% | 6.1% |
| Age 10 to 14 | 7.0% | 5.3% | 6.6% |
| Age 15 to 17 | 4.4% | 3.1% | 3.9% |
| Age 18 to 20 | 2.5% | 9.5% | 4.0% |
| Age 21 to 24 | 3.5% | 12.5% | 5.2% |
| Age 25 to 34 | 12.3% | 18.2% | 13.8% |
| Age 35 to 44 | 15.2% | 11.9% | 12.9% |
| Age 45 to 54 | 14.8% | 9.4% | 12.6% |
| Age 55 to 59 | 5.8% | 5.1% | 6.7% |
| Age 60 to 64 | 6.0% | 4.8% | 6.3% |
| Age 65 to 74 | 9.7% | 6.7% | 9.6% |
| Age 75 to 84 | 4.6% | 3.0% | 4.5% |
| Age 85 and over | 1.5% | 1.4% | 1.9% |
| space1 | | | |
| Race | | | |
| | Oak Park, IL | Fort Collins, CO | United States |
| White | 60.4% | 78.1% | 59.4% |
| Black | 18.2% | 1.3% | 12.2% |
| Asian | 5.3% | 3.2% | 5.6% |
| Native American | 0.1% | 0.6% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.1% | 0.2% |
| Other | 0.6% | 0.4% | 0.4% |
| Two or More Races | 5.5% | 3.7% | 3.2% |
| Hispanic | 9.9% | 12.6% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Oak Park, IL | Fort Collins, CO | United States |
| Married Population | 49.8% | 41.6% | 49.8% |
| Currently Married | 49.1% | 40.9% | 48.0% |
| Married but Separated | 0.7% | 0.7% | 1.8% |
| Single Population | 50.2% | 58.4% | 50.2% |
| Never Married | 35.9% | 46.6% | 33.8% |
| Divorced | 9.6% | 8.5% | 10.8% |
| Widowed | 4.6% | 3.3% | 5.6% |
| space5 | | | |
| Household Size | 2.35 | 2.36 | 2.60 |
| Households | 22,793 | 67,270 | 124,010,992 |
| Family Households | 13,227 | 35,069 | 80,755,759 |
| Married couple, w/children | 38.8% | 33.6% | 30.5% |
| Married couple, no children | 38.4% | 46.3% | 42.9% |
| Non Family Households | 9,566 | 32,201 | 43,255,233 |
| Single householder, w/children | 13.6% | 12.1% | 15.8% |
| Single householder, no children | 9.2% | 8.0% | 10.8% |