| PEOPLE | Rock Falls | Elmhurst | United States |
| Population | 9,266 | 44,121 | 308,035,306 |
| Pop. Density | 2,535 | 4,303 | 87 |
| Pop. Change | -4.70% | 2.20% | 8.07% |
| Median Age | 38.6 | 40.1 | 37.3 |
| Households | 3,809 | 15,765 | 116,716,292 |
| Household Size | 2.38 | 2.73 | 2.58 |
| Male Population | 48.35% | 48.23% | 49.27% |
| Female Population | 51.65% | 51.77% | 50.96% |
| Married Population | 44.50% | 56.32% | 47.02% |
| Single Population | 55.50% | 43.68% | 52.98% |
| ESTIMATED TOTAL POPULATION BY AGE | | | |
| Age 0 to 4 | 7.38% | 6.11% | 6.56% |
| Age 5 to 9 | 6.95% | 7.91% | 6.61% |
| Age 10 to 14 | 6.81% | 7.86% | 6.71% |
| Age 15 to 17 | 4.10% | 4.65% | 4.21% |
| Age 18 to 20 | 2.34% | 3.23% | 2.95% |
| Age 21 to 24 | 6.23% | 5.95% | 7.01% |
| Age 25 to 34 | 11.95% | 7.94% | 13.33% |
| Age 35 to 44 | 12.37% | 13.97% | 13.33% |
| Age 45 to 49 | 13.95% | 16.57% | 14.61% |
| Age 50 to 54 | 13.95% | 16.57% | 14.61% |
| Age 55 to 59 | 12.20% | 11.44% | 11.84% |
| Age 60 to 64 | 12.20% | 11.44% | 11.84% |
| Age 65 to 74 | 8.16% | 6.70% | 7.05% |
| Age 75 to 84 | 5.27% | 4.85% | 4.24% |
| Age 85 and over | 2.30% | 2.82% | 1.78% |
| RACE | | | |
| White | 91.46% | 89.48% | 72.41% |
| Black | 1.49% | 1.91% | 12.61% |
| Asian | 0.30% | 5.15% | 4.75% |
| American Indian | 0.42% | 0.12% | 0.95% |
| Other | 6.32% | 3.35% | 9.28% |
| Hispanic | 1.71% | 5.37% | 16.35% |
| Non-Hispanic | 98.29% | 94.63% | 83.65% |
| FAMILY | | | |
| Married, w/children | 22.20% | 42.46% | 30.42% |
| Married, no children | 42.44% | 42.20% | 42.46% |
| Single, w/children | 22.12% | 6.64% | 14.39% |
| Single, no children | 13.24% | 8.71% | 12.73% |
| Divorced | 17.86% | 7.31% | 10.62% |
| Separated | 2.93% | 2.73% | 4.97% |
| Widowed | 8.79% | 7.31% | 6.14% |
| Now Married | 44.32% | 55.89% | 46.32% |
| Never Married | 26.10% | 26.76% | 31.95% |
