| | Northlake, IL | Leesburg, FL | United States |
| Population | 12,836 | 26,242 | 329,725,481 |
| Female Population | 52.2% | 53.2% | 50.5% |
| Male Population | 47.9% | 46.8% | 49.5% |
| Median Age | 37.7 | 42.9 | 38.4 |
| space3 | | | |
| Population - 2010 | 12,341 | 20,416 | 309,327,143 |
| Population - 2000 | 11,878 | 15,956 | 285,036,114 |
| Population - 1990 | 12,505 | 14,903 | 251,960,433 |
| Pop. 2000 to Now | 1.2% | 50.8% | 15.6% |
| Pop. 1990 to Now | -3.8% | 61.4% | 30.8% |
| space4 | | | |
| Population Density | 4,046.7 | 716.6 | 93.4 |
| Land Area | 3.2 | 36.6 | 3,531,905.4 |
| Water Area | 0.0 | 3.4 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Northlake, IL | Leesburg, FL | United States |
| Age 0 to 4 | 3.2% | 4.2% | 5.9% |
| Age 5 to 9 | 6.5% | 7.1% | 6.1% |
| Age 10 to 14 | 7.8% | 6.6% | 6.6% |
| Age 15 to 17 | 5.1% | 3.5% | 3.9% |
| Age 18 to 20 | 4.6% | 3.9% | 4.0% |
| Age 21 to 24 | 4.9% | 4.1% | 5.2% |
| Age 25 to 34 | 12.9% | 12.7% | 13.8% |
| Age 35 to 44 | 16.2% | 12.5% | 12.9% |
| Age 45 to 54 | 12.0% | 9.6% | 12.6% |
| Age 55 to 59 | 7.4% | 4.2% | 6.7% |
| Age 60 to 64 | 5.2% | 6.2% | 6.3% |
| Age 65 to 74 | 9.0% | 15.5% | 9.6% |
| Age 75 to 84 | 3.1% | 6.5% | 4.5% |
| Age 85 and over | 2.1% | 3.5% | 1.9% |
| space1 | | | |
| Race | | | |
| | Northlake, IL | Leesburg, FL | United States |
| White | 32.1% | 50.4% | 59.4% |
| Black | 3.3% | 23.0% | 12.2% |
| Asian | 2.3% | 1.3% | 5.6% |
| Native American | 0.0% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.2% | 0.0% | 0.4% |
| Two or More Races | 0.8% | 1.8% | 3.2% |
| Hispanic | 61.3% | 23.4% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Northlake, IL | Leesburg, FL | United States |
| Married Population | 41.1% | 45.5% | 49.8% |
| Currently Married | 38.5% | 43.2% | 48.0% |
| Married but Separated | 2.6% | 2.2% | 1.8% |
| Single Population | 58.9% | 54.5% | 50.2% |
| Never Married | 41.8% | 33.9% | 33.8% |
| Divorced | 10.3% | 12.1% | 10.8% |
| Widowed | 6.9% | 8.5% | 5.6% |
| space5 | | | |
| Household Size | 2.79 | 2.39 | 2.60 |
| Households | 4,481 | 10,778 | 124,010,992 |
| Family Households | 3,061 | 6,642 | 80,755,759 |
| Married couple, w/children | 23.8% | 17.2% | 30.5% |
| Married couple, no children | 32.9% | 49.3% | 42.9% |
| Non Family Households | 1,420 | 4,136 | 43,255,233 |
| Single householder, w/children | 21.9% | 22.0% | 15.8% |
| Single householder, no children | 21.5% | 11.5% | 10.8% |