| | Marcus, IA | United States, IA |
| Population | 1,106 | 329,725,481 |
| Female Population | 49.8% | 50.5% |
| Male Population | 50.2% | 49.5% |
| Median Age | 51.3 | 38.4 |
| space3 | | |
| Population - 2010 | 1,119 | 309,327,143 |
| Population - 2000 | 1,139 | 285,036,114 |
| Population - 1990 | 1,171 | 251,960,433 |
| Pop. 2000 to Now | -7.4% | 15.6% |
| Pop. 1990 to Now | -9.9% | 30.8% |
| space4 | | |
| Population Density | 719.6 | 93.4 |
| Land Area | 1.5 | 3,531,905.4 |
| Water Area | 0.0 | 264,836.8 |
| space | | |
| Est. Total Population By Age | | |
| | Marcus, IA | Marcus, IA |
| Age 0 to 4 | 4.0% | 5.9% |
| Age 5 to 9 | 4.3% | 6.1% |
| Age 10 to 14 | 3.7% | 6.6% |
| Age 15 to 17 | 2.0% | 3.9% |
| Age 18 to 20 | 1.9% | 4.0% |
| Age 21 to 24 | 6.8% | 5.2% |
| Age 25 to 34 | 10.3% | 13.8% |
| Age 35 to 44 | 13.0% | 12.9% |
| Age 45 to 54 | 7.1% | 12.6% |
| Age 55 to 59 | 4.4% | 6.7% |
| Age 60 to 64 | 10.9% | 6.3% |
| Age 65 to 74 | 13.1% | 9.6% |
| Age 75 to 84 | 9.3% | 4.5% |
| Age 85 and over | 9.2% | 1.9% |
| space1 | | |
| Race | | |
| | Marcus, IA | Marcus, IA |
| White | 82.3% | 59.4% |
| Black | 10.7% | 12.2% |
| Asian | 0.0% | 5.6% |
| Native American | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.2% |
| Other | 0.0% | 0.4% |
| Two or More Races | 3.5% | 3.2% |
| Hispanic | 3.5% | 18.4% |
| space2 | | |
| Marriage & Family | | |
| | Marcus, IA | Marcus, IA |
| Married Population | 57.1% | 49.8% |
| Currently Married | 57.1% | 48.0% |
| Married but Separated | 0.0% | 1.8% |
| Single Population | 42.9% | 50.2% |
| Never Married | 23.9% | 33.8% |
| Divorced | 6.5% | 10.8% |
| Widowed | 12.5% | 5.6% |
| space5 | | |
| Household Size | 2.03 | 2.60 |
| Households | 532 | 124,010,992 |
| Family Households | 278 | 80,755,759 |
| Married couple, w/children | 15.5% | 30.5% |
| Married couple, no children | 72.7% | 42.9% |
| Non Family Households | 254 | 43,255,233 |
| Single householder, w/children | 10.1% | 15.8% |
| Single householder, no children | 1.8% | 10.8% |