| | Oconee, IL | Fillmore, IL | United States |
| Population | 168 | 257 | 329,725,481 |
| Female Population | 53.0% | 50.6% | 50.5% |
| Male Population | 47.0% | 49.4% | 49.5% |
| Median Age | 36.9 | 53.1 | 38.4 |
| space3 | | | |
| Population - 2010 | 180 | 330 | 309,327,143 |
| Population - 2000 | 202 | 362 | 285,036,114 |
| Population - 1990 | 201 | 326 | 251,960,433 |
| Pop. 2000 to Now | -16.3% | -15.8% | 15.6% |
| Pop. 1990 to Now | -15.9% | -6.4% | 30.8% |
| space4 | | | |
| Population Density | 471.9 | 254.2 | 93.4 |
| Land Area | 0.4 | 1.0 | 3,531,905.4 |
| Water Area | 0.0 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Oconee, IL | Fillmore, IL | United States |
| Age 0 to 4 | 8.3% | 1.6% | 5.9% |
| Age 5 to 9 | 7.1% | 1.6% | 6.1% |
| Age 10 to 14 | 5.4% | 5.1% | 6.6% |
| Age 15 to 17 | 1.8% | 2.3% | 3.9% |
| Age 18 to 20 | 1.2% | 2.7% | 4.0% |
| Age 21 to 24 | 3.0% | 4.7% | 5.2% |
| Age 25 to 34 | 17.3% | 8.6% | 13.8% |
| Age 35 to 44 | 14.9% | 8.6% | 12.9% |
| Age 45 to 54 | 11.3% | 19.1% | 12.6% |
| Age 55 to 59 | 1.8% | 9.7% | 6.7% |
| Age 60 to 64 | 4.2% | 9.7% | 6.3% |
| Age 65 to 74 | 15.5% | 15.2% | 9.6% |
| Age 75 to 84 | 2.4% | 8.9% | 4.5% |
| Age 85 and over | 6.0% | 2.3% | 1.9% |
| space1 | | | |
| Race | | | |
| | Oconee, IL | Fillmore, IL | United States |
| White | 94.0% | 95.3% | 59.4% |
| Black | 0.0% | 0.0% | 12.2% |
| Asian | 0.0% | 1.9% | 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 | 4.2% | 2.7% | 3.2% |
| Hispanic | 1.8% | 0.0% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Oconee, IL | Fillmore, IL | United States |
| Married Population | 62.4% | 55.9% | 49.8% |
| Currently Married | 60.9% | 55.9% | 48.0% |
| Married but Separated | 1.5% | 0.0% | 1.8% |
| Single Population | 37.6% | 44.1% | 50.2% |
| Never Married | 15.0% | 20.3% | 33.8% |
| Divorced | 18.0% | 13.6% | 10.8% |
| Widowed | 4.5% | 10.2% | 5.6% |
| space5 | | | |
| Household Size | 2.37 | 2.02 | 2.60 |
| Households | 71 | 127 | 124,010,992 |
| Family Households | 47 | 69 | 80,755,759 |
| Married couple, w/children | 36.2% | 14.5% | 30.5% |
| Married couple, no children | 46.8% | 78.3% | 42.9% |
| Non Family Households | 24 | 58 | 43,255,233 |
| Single householder, w/children | 10.6% | 1.4% | 15.8% |
| Single householder, no children | 6.4% | 5.8% | 10.8% |