| | Sandusky, OH | Marquette, MI | United States |
| Population | 25,066 | 20,561 | 329,725,481 |
| Female Population | 53.1% | 49.3% | 50.5% |
| Male Population | 46.9% | 50.7% | 49.5% |
| Median Age | 36.9 | 30.2 | 38.4 |
| space3 | | | |
| Population - 2010 | 25,871 | 21,357 | 309,327,143 |
| Population - 2000 | 27,844 | 19,661 | 285,036,114 |
| Population - 1990 | 29,764 | 21,977 | 251,960,433 |
| Pop. 2000 to Now | -12.7% | 3.3% | 15.6% |
| Pop. 1990 to Now | -18.3% | -7.6% | 30.8% |
| space4 | | | |
| Population Density | 2,580.4 | 1,813.6 | 93.4 |
| Land Area | 9.7 | 11.3 | 3,531,905.4 |
| Water Area | 12.2 | 8.1 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Sandusky, OH | Marquette, MI | United States |
| Age 0 to 4 | 7.2% | 3.4% | 5.9% |
| Age 5 to 9 | 6.3% | 3.1% | 6.1% |
| Age 10 to 14 | 5.9% | 2.9% | 6.6% |
| Age 15 to 17 | 3.7% | 1.8% | 3.9% |
| Age 18 to 20 | 3.3% | 12.9% | 4.0% |
| Age 21 to 24 | 5.4% | 17.4% | 5.2% |
| Age 25 to 34 | 16.5% | 14.4% | 13.8% |
| Age 35 to 44 | 10.5% | 8.5% | 12.9% |
| Age 45 to 54 | 12.3% | 9.6% | 12.6% |
| Age 55 to 59 | 6.8% | 5.3% | 6.7% |
| Age 60 to 64 | 6.9% | 5.0% | 6.3% |
| Age 65 to 74 | 9.3% | 9.1% | 9.6% |
| Age 75 to 84 | 4.1% | 4.4% | 4.5% |
| Age 85 and over | 1.9% | 2.3% | 1.9% |
| space1 | | | |
| Race | | | |
| | Sandusky, OH | Marquette, MI | United States |
| White | 63.3% | 89.1% | 59.4% |
| Black | 22.0% | 3.5% | 12.2% |
| Asian | 0.4% | 0.4% | 5.6% |
| Native American | 0.5% | 0.4% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.1% | 0.2% |
| Other | 0.2% | 0.2% | 0.4% |
| Two or More Races | 5.9% | 3.8% | 3.2% |
| Hispanic | 7.6% | 2.5% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Sandusky, OH | Marquette, MI | United States |
| Married Population | 36.2% | 30.1% | 49.8% |
| Currently Married | 34.0% | 29.8% | 48.0% |
| Married but Separated | 2.2% | 0.3% | 1.8% |
| Single Population | 63.8% | 69.9% | 50.2% |
| Never Married | 42.5% | 55.8% | 33.8% |
| Divorced | 14.2% | 9.2% | 10.8% |
| Widowed | 7.1% | 4.9% | 5.6% |
| space5 | | | |
| Household Size | 2.20 | 2.17 | 2.60 |
| Households | 11,167 | 8,163 | 124,010,992 |
| Family Households | 6,381 | 3,651 | 80,755,759 |
| Married couple, w/children | 14.6% | 18.9% | 30.5% |
| Married couple, no children | 36.0% | 52.6% | 42.9% |
| Non Family Households | 4,786 | 4,512 | 43,255,233 |
| Single householder, w/children | 34.0% | 16.5% | 15.8% |
| Single householder, no children | 15.3% | 12.0% | 10.8% |