| | Countryside, IL | Milton, WI | United States |
| Population | 6,354 | 5,708 | 329,725,481 |
| Female Population | 50.4% | 50.0% | 50.5% |
| Male Population | 49.7% | 50.1% | 49.5% |
| Median Age | 47.3 | 38.4 | 38.4 |
| space3 | | | |
| Population - 2010 | 5,923 | 5,548 | 309,327,143 |
| Population - 2000 | 5,991 | 5,132 | 285,036,114 |
| Population - 1990 | 5,716 | 4,434 | 251,960,433 |
| Pop. 2000 to Now | -2.2% | 10.0% | 15.6% |
| Pop. 1990 to Now | 2.6% | 27.3% | 30.8% |
| space4 | | | |
| Population Density | 2,207.8 | 1,339.9 | 93.4 |
| Land Area | 2.9 | 4.3 | 3,531,905.4 |
| Water Area | 0.0 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Countryside, IL | Milton, WI | United States |
| Age 0 to 4 | 4.1% | 2.8% | 5.9% |
| Age 5 to 9 | 2.4% | 6.5% | 6.1% |
| Age 10 to 14 | 7.6% | 6.8% | 6.6% |
| Age 15 to 17 | 5.2% | 7.3% | 3.9% |
| Age 18 to 20 | 3.4% | 3.5% | 4.0% |
| Age 21 to 24 | 5.9% | 6.2% | 5.2% |
| Age 25 to 34 | 11.6% | 12.3% | 13.8% |
| Age 35 to 44 | 7.4% | 16.7% | 12.9% |
| Age 45 to 54 | 15.6% | 13.2% | 12.6% |
| Age 55 to 59 | 9.6% | 3.5% | 6.7% |
| Age 60 to 64 | 8.0% | 5.9% | 6.3% |
| Age 65 to 74 | 12.3% | 9.0% | 9.6% |
| Age 75 to 84 | 4.3% | 5.3% | 4.5% |
| Age 85 and over | 2.7% | 1.1% | 1.9% |
| space1 | | | |
| Race | | | |
| | Countryside, IL | Milton, WI | United States |
| White | 69.6% | 90.5% | 59.4% |
| Black | 2.2% | 0.4% | 12.2% |
| Asian | 2.3% | 0.0% | 5.6% |
| Native American | 0.0% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.4% | 0.0% | 0.4% |
| Two or More Races | 1.3% | 3.9% | 3.2% |
| Hispanic | 24.2% | 5.2% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Countryside, IL | Milton, WI | United States |
| Married Population | 44.3% | 53.5% | 49.8% |
| Currently Married | 42.6% | 53.5% | 48.0% |
| Married but Separated | 1.7% | 0.0% | 1.8% |
| Single Population | 55.7% | 46.5% | 50.2% |
| Never Married | 38.0% | 30.7% | 33.8% |
| Divorced | 13.1% | 12.1% | 10.8% |
| Widowed | 4.7% | 3.8% | 5.6% |
| space5 | | | |
| Household Size | 2.33 | 2.54 | 2.60 |
| Households | 2,713 | 2,244 | 124,010,992 |
| Family Households | 1,683 | 1,510 | 80,755,759 |
| Married couple, w/children | 29.6% | 37.1% | 30.5% |
| Married couple, no children | 37.3% | 44.7% | 42.9% |
| Non Family Households | 1,030 | 734 | 43,255,233 |
| Single householder, w/children | 9.9% | 10.1% | 15.8% |
| Single householder, no children | 23.2% | 8.1% | 10.8% |