| | St. Clair, MI | Gurnee, IL | United States |
| Population | 5,489 | 30,826 | 329,725,481 |
| Female Population | 51.6% | 52.9% | 50.5% |
| Male Population | 48.4% | 47.1% | 49.5% |
| Median Age | 41.4 | 40 | 38.4 |
| space3 | | | |
| Population - 2010 | 5,465 | 31,256 | 309,327,143 |
| Population - 2000 | 5,802 | 28,834 | 285,036,114 |
| Population - 1990 | 5,116 | 13,701 | 251,960,433 |
| Pop. 2000 to Now | -5.3% | 4.6% | 15.6% |
| Pop. 1990 to Now | 7.4% | 120.2% | 30.8% |
| space4 | | | |
| Population Density | 1,867.0 | 2,282.9 | 93.4 |
| Land Area | 2.9 | 13.5 | 3,531,905.4 |
| Water Area | 0.7 | 0.1 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | St. Clair, MI | Gurnee, IL | United States |
| Age 0 to 4 | 2.9% | 4.1% | 5.9% |
| Age 5 to 9 | 3.8% | 7.1% | 6.1% |
| Age 10 to 14 | 12.1% | 5.8% | 6.6% |
| Age 15 to 17 | 3.2% | 4.7% | 3.9% |
| Age 18 to 20 | 4.4% | 5.6% | 4.0% |
| Age 21 to 24 | 5.6% | 5.6% | 5.2% |
| Age 25 to 34 | 11.6% | 11.2% | 13.8% |
| Age 35 to 44 | 10.7% | 12.2% | 12.9% |
| Age 45 to 54 | 15.6% | 16.8% | 12.6% |
| Age 55 to 59 | 7.4% | 7.6% | 6.7% |
| Age 60 to 64 | 5.8% | 6.8% | 6.3% |
| Age 65 to 74 | 9.0% | 7.9% | 9.6% |
| Age 75 to 84 | 5.8% | 3.3% | 4.5% |
| Age 85 and over | 2.0% | 1.3% | 1.9% |
| space1 | | | |
| Race | | | |
| | St. Clair, MI | Gurnee, IL | United States |
| White | 94.2% | 61.5% | 59.4% |
| Black | 1.8% | 7.1% | 12.2% |
| Asian | 0.9% | 12.5% | 5.6% |
| Native American | 0.0% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.3% | 0.4% |
| Two or More Races | 1.1% | 3.2% | 3.2% |
| Hispanic | 2.0% | 15.4% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | St. Clair, MI | Gurnee, IL | United States |
| Married Population | 56.1% | 55.1% | 49.8% |
| Currently Married | 55.1% | 54.3% | 48.0% |
| Married but Separated | 1.0% | 0.8% | 1.8% |
| Single Population | 43.9% | 44.9% | 50.2% |
| Never Married | 29.4% | 32.5% | 33.8% |
| Divorced | 8.6% | 7.7% | 10.8% |
| Widowed | 5.8% | 4.7% | 5.6% |
| space5 | | | |
| Household Size | 2.54 | 2.65 | 2.60 |
| Households | 2,147 | 11,630 | 124,010,992 |
| Family Households | 1,551 | 8,134 | 80,755,759 |
| Married couple, w/children | 29.1% | 36.3% | 30.5% |
| Married couple, no children | 47.5% | 45.7% | 42.9% |
| Non Family Households | 596 | 3,496 | 43,255,233 |
| Single householder, w/children | 12.6% | 10.1% | 15.8% |
| Single householder, no children | 10.8% | 7.9% | 10.8% |