| | Waterloo, IL | Troy, IL | United States |
| Population | 10,906 | 10,858 | 329,725,481 |
| Female Population | 51.2% | 56.0% | 50.5% |
| Male Population | 48.8% | 44.0% | 49.5% |
| Median Age | 40.4 | 37.9 | 38.4 |
| space3 | | | |
| Population - 2010 | 9,970 | 9,929 | 309,327,143 |
| Population - 2000 | 7,614 | 8,524 | 285,036,114 |
| Population - 1990 | 5,072 | 6,046 | 251,960,433 |
| Pop. 2000 to Now | 38.4% | 22.0% | 15.6% |
| Pop. 1990 to Now | 107.7% | 72.0% | 30.8% |
| space4 | | | |
| Population Density | 1,340.3 | 1,959.2 | 93.4 |
| Land Area | 8.1 | 5.5 | 3,531,905.4 |
| Water Area | 0.1 | 0.1 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Waterloo, IL | Troy, IL | United States |
| Age 0 to 4 | 6.7% | 7.7% | 5.9% |
| Age 5 to 9 | 6.1% | 6.1% | 6.1% |
| Age 10 to 14 | 7.6% | 6.7% | 6.6% |
| Age 15 to 17 | 1.8% | 4.2% | 3.9% |
| Age 18 to 20 | 1.7% | 2.3% | 4.0% |
| Age 21 to 24 | 4.9% | 2.3% | 5.2% |
| Age 25 to 34 | 12.4% | 14.1% | 13.8% |
| Age 35 to 44 | 15.1% | 15.4% | 12.9% |
| Age 45 to 54 | 9.6% | 14.1% | 12.6% |
| Age 55 to 59 | 6.2% | 8.0% | 6.7% |
| Age 60 to 64 | 7.5% | 6.2% | 6.3% |
| Age 65 to 74 | 11.4% | 7.3% | 9.6% |
| Age 75 to 84 | 5.3% | 3.5% | 4.5% |
| Age 85 and over | 3.7% | 2.1% | 1.9% |
| space1 | | | |
| Race | | | |
| | Waterloo, IL | Troy, IL | United States |
| White | 95.3% | 89.9% | 59.4% |
| Black | 0.5% | 2.1% | 12.2% |
| Asian | 1.6% | 1.3% | 5.6% |
| Native American | 0.5% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.0% | 0.4% |
| Two or More Races | 0.7% | 3.5% | 3.2% |
| Hispanic | 1.5% | 3.2% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Waterloo, IL | Troy, IL | United States |
| Married Population | 56.4% | 59.1% | 49.8% |
| Currently Married | 55.7% | 57.9% | 48.0% |
| Married but Separated | 0.7% | 1.2% | 1.8% |
| Single Population | 43.6% | 40.9% | 50.2% |
| Never Married | 22.9% | 23.4% | 33.8% |
| Divorced | 13.4% | 11.8% | 10.8% |
| Widowed | 7.3% | 5.6% | 5.6% |
| space5 | | | |
| Household Size | 2.47 | 2.51 | 2.60 |
| Households | 4,366 | 4,203 | 124,010,992 |
| Family Households | 3,068 | 2,714 | 80,755,759 |
| Married couple, w/children | 30.9% | 39.3% | 30.5% |
| Married couple, no children | 48.0% | 46.8% | 42.9% |
| Non Family Households | 1,298 | 1,489 | 43,255,233 |
| Single householder, w/children | 13.4% | 8.7% | 15.8% |
| Single householder, no children | 7.7% | 5.2% | 10.8% |