| | Island Lake, IL | Bettendorf, IA | United States |
| Population | 8,057 | 38,631 | 329,725,481 |
| Female Population | 50.6% | 52.0% | 50.5% |
| Male Population | 49.4% | 48.0% | 49.5% |
| Median Age | 39.9 | 38.9 | 38.4 |
| space3 | | | |
| Population - 2010 | 8,074 | 33,281 | 309,327,143 |
| Population - 2000 | 8,153 | 31,275 | 285,036,114 |
| Population - 1990 | 4,449 | 28,132 | 251,960,433 |
| Pop. 2000 to Now | -2.5% | 17.2% | 15.6% |
| Pop. 1990 to Now | 78.7% | 30.3% | 30.8% |
| space4 | | | |
| Population Density | 2,361.4 | 1,813.9 | 93.4 |
| Land Area | 3.4 | 21.3 | 3,531,905.4 |
| Water Area | 0.2 | 1.1 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Island Lake, IL | Bettendorf, IA | United States |
| Age 0 to 4 | 9.0% | 6.2% | 5.9% |
| Age 5 to 9 | 5.3% | 8.0% | 6.1% |
| Age 10 to 14 | 4.9% | 7.3% | 6.6% |
| Age 15 to 17 | 3.2% | 4.5% | 3.9% |
| Age 18 to 20 | 3.5% | 3.7% | 4.0% |
| Age 21 to 24 | 4.2% | 2.6% | 5.2% |
| Age 25 to 34 | 11.8% | 11.7% | 13.8% |
| Age 35 to 44 | 13.8% | 14.3% | 12.9% |
| Age 45 to 54 | 14.5% | 13.0% | 12.6% |
| Age 55 to 59 | 9.0% | 5.7% | 6.7% |
| Age 60 to 64 | 5.8% | 6.0% | 6.3% |
| Age 65 to 74 | 10.6% | 10.0% | 9.6% |
| Age 75 to 84 | 2.6% | 5.6% | 4.5% |
| Age 85 and over | 1.8% | 1.4% | 1.9% |
| space1 | | | |
| Race | | | |
| | Island Lake, IL | Bettendorf, IA | United States |
| White | 78.0% | 83.5% | 59.4% |
| Black | 0.2% | 1.8% | 12.2% |
| Asian | 3.0% | 6.4% | 5.6% |
| Native American | 0.0% | 0.1% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.2% | 0.4% |
| Two or More Races | 1.5% | 3.5% | 3.2% |
| Hispanic | 17.2% | 4.6% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Island Lake, IL | Bettendorf, IA | United States |
| Married Population | 53.3% | 56.6% | 49.8% |
| Currently Married | 52.6% | 55.4% | 48.0% |
| Married but Separated | 0.7% | 1.3% | 1.8% |
| Single Population | 46.7% | 43.4% | 50.2% |
| Never Married | 26.6% | 25.4% | 33.8% |
| Divorced | 16.0% | 12.9% | 10.8% |
| Widowed | 4.1% | 5.1% | 5.6% |
| space5 | | | |
| Household Size | 2.66 | 2.51 | 2.60 |
| Households | 3,004 | 15,311 | 124,010,992 |
| Family Households | 2,004 | 10,374 | 80,755,759 |
| Married couple, w/children | 35.4% | 38.6% | 30.5% |
| Married couple, no children | 45.1% | 41.1% | 42.9% |
| Non Family Households | 1,000 | 4,937 | 43,255,233 |
| Single householder, w/children | 10.2% | 15.0% | 15.8% |
| Single householder, no children | 9.4% | 5.4% | 10.8% |