| | Rensselaer, IN | Watseka, IL | United States |
| Population | 5,963 | 4,623 | 329,725,481 |
| Female Population | 52.3% | 55.2% | 50.5% |
| Male Population | 47.7% | 44.8% | 49.5% |
| Median Age | 37.4 | 50.3 | 38.4 |
| space3 | | | |
| Population - 2010 | 5,993 | 5,286 | 309,327,143 |
| Population - 2000 | 5,294 | 5,670 | 285,036,114 |
| Population - 1990 | 5,045 | 5,424 | 251,960,433 |
| Pop. 2000 to Now | 9.2% | -17.2% | 15.6% |
| Pop. 1990 to Now | 14.6% | -13.5% | 30.8% |
| space4 | | | |
| Population Density | 906.4 | 1,497.6 | 93.4 |
| Land Area | 6.6 | 3.1 | 3,531,905.4 |
| Water Area | 0.1 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Rensselaer, IN | Watseka, IL | United States |
| Age 0 to 4 | 5.8% | 4.8% | 5.9% |
| Age 5 to 9 | 7.5% | 3.4% | 6.1% |
| Age 10 to 14 | 7.5% | 2.4% | 6.6% |
| Age 15 to 17 | 3.3% | 6.0% | 3.9% |
| Age 18 to 20 | 3.4% | 2.6% | 4.0% |
| Age 21 to 24 | 4.2% | 6.8% | 5.2% |
| Age 25 to 34 | 15.1% | 7.4% | 13.8% |
| Age 35 to 44 | 11.9% | 10.7% | 12.9% |
| Age 45 to 54 | 12.5% | 12.1% | 12.6% |
| Age 55 to 59 | 6.2% | 6.0% | 6.7% |
| Age 60 to 64 | 5.8% | 11.9% | 6.3% |
| Age 65 to 74 | 10.3% | 13.2% | 9.6% |
| Age 75 to 84 | 4.5% | 7.9% | 4.5% |
| Age 85 and over | 2.0% | 4.4% | 1.9% |
| space1 | | | |
| Race | | | |
| | Rensselaer, IN | Watseka, IL | United States |
| White | 87.9% | 91.8% | 59.4% |
| Black | 1.8% | 0.7% | 12.2% |
| Asian | 0.2% | 1.1% | 5.6% |
| Native American | 0.0% | 0.2% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 1.1% | 0.4% |
| Two or More Races | 2.8% | 0.4% | 3.2% |
| Hispanic | 7.4% | 4.6% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Rensselaer, IN | Watseka, IL | United States |
| Married Population | 47.0% | 39.2% | 49.8% |
| Currently Married | 46.6% | 38.1% | 48.0% |
| Married but Separated | 0.4% | 1.0% | 1.8% |
| Single Population | 53.0% | 60.8% | 50.2% |
| Never Married | 25.3% | 28.4% | 33.8% |
| Divorced | 20.9% | 20.3% | 10.8% |
| Widowed | 6.8% | 12.1% | 5.6% |
| space5 | | | |
| Household Size | 2.37 | 2.09 | 2.60 |
| Households | 2,427 | 2,143 | 124,010,992 |
| Family Households | 1,339 | 1,079 | 80,755,759 |
| Married couple, w/children | 31.7% | 18.6% | 30.5% |
| Married couple, no children | 39.1% | 51.9% | 42.9% |
| Non Family Households | 1,088 | 1,064 | 43,255,233 |
| Single householder, w/children | 19.7% | 14.3% | 15.8% |
| Single householder, no children | 9.5% | 15.2% | 10.8% |