| | Rock Falls, IL | Naperville, IL | United States |
| Population | 8,807 | 149,013 | 329,725,481 |
| Female Population | 52.0% | 50.5% | 50.5% |
| Male Population | 48.0% | 49.5% | 49.5% |
| Median Age | 39.4 | 39.3 | 38.4 |
| space3 | | | |
| Population - 2010 | 9,394 | 142,408 | 309,327,143 |
| Population - 2000 | 9,580 | 128,358 | 285,036,114 |
| Population - 1990 | 9,654 | 85,351 | 251,960,433 |
| Pop. 2000 to Now | -9.7% | 15.3% | 15.6% |
| Pop. 1990 to Now | -10.4% | 73.4% | 30.8% |
| space4 | | | |
| Population Density | 2,212.8 | 3,839.6 | 93.4 |
| Land Area | 4.0 | 38.8 | 3,531,905.4 |
| Water Area | 0.1 | 0.6 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Rock Falls, IL | Naperville, IL | United States |
| Age 0 to 4 | 6.6% | 6.0% | 5.9% |
| Age 5 to 9 | 4.3% | 6.5% | 6.1% |
| Age 10 to 14 | 8.7% | 7.8% | 6.6% |
| Age 15 to 17 | 4.7% | 4.9% | 3.9% |
| Age 18 to 20 | 3.4% | 3.2% | 4.0% |
| Age 21 to 24 | 4.5% | 4.2% | 5.2% |
| Age 25 to 34 | 11.9% | 11.3% | 13.8% |
| Age 35 to 44 | 12.0% | 14.2% | 12.9% |
| Age 45 to 54 | 11.4% | 15.0% | 12.6% |
| Age 55 to 59 | 5.2% | 7.6% | 6.7% |
| Age 60 to 64 | 10.2% | 5.9% | 6.3% |
| Age 65 to 74 | 10.2% | 8.3% | 9.6% |
| Age 75 to 84 | 4.7% | 3.5% | 4.5% |
| Age 85 and over | 2.2% | 1.5% | 1.9% |
| space1 | | | |
| Race | | | |
| | Rock Falls, IL | Naperville, IL | United States |
| White | 77.3% | 65.1% | 59.4% |
| Black | 0.4% | 4.3% | 12.2% |
| Asian | 0.1% | 20.6% | 5.6% |
| Native American | 0.4% | 0.1% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.3% | 0.4% |
| Two or More Races | 0.4% | 3.2% | 3.2% |
| Hispanic | 21.6% | 6.5% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Rock Falls, IL | Naperville, IL | United States |
| Married Population | 40.3% | 61.8% | 49.8% |
| Currently Married | 38.9% | 60.9% | 48.0% |
| Married but Separated | 1.4% | 0.9% | 1.8% |
| Single Population | 59.7% | 38.2% | 50.2% |
| Never Married | 34.5% | 27.2% | 33.8% |
| Divorced | 16.8% | 7.0% | 10.8% |
| Widowed | 8.4% | 4.0% | 5.6% |
| space5 | | | |
| Household Size | 2.25 | 2.75 | 2.60 |
| Households | 3,871 | 53,234 | 124,010,992 |
| Family Households | 2,114 | 39,815 | 80,755,759 |
| Married couple, w/children | 25.3% | 42.3% | 30.5% |
| Married couple, no children | 31.6% | 43.9% | 42.9% |
| Non Family Households | 1,757 | 13,419 | 43,255,233 |
| Single householder, w/children | 29.6% | 8.4% | 15.8% |
| Single householder, no children | 13.6% | 5.3% | 10.8% |