| | Marengo, IN | Salem, IN | United States |
| Population | 732 | 6,276 | 329,725,481 |
| Female Population | 49.2% | 52.1% | 50.5% |
| Male Population | 50.8% | 47.9% | 49.5% |
| Median Age | 37.6 | 37.9 | 38.4 |
| space3 | | | |
| Population - 2010 | 825 | 6,323 | 309,327,143 |
| Population - 2000 | 829 | 6,172 | 285,036,114 |
| Population - 1990 | 856 | 5,619 | 251,960,433 |
| Pop. 2000 to Now | -2.5% | 1.0% | 15.6% |
| Pop. 1990 to Now | -5.6% | 11.0% | 30.8% |
| space4 | | | |
| Population Density | 945.7 | 1,569.0 | 93.4 |
| Land Area | 0.8 | 4.0 | 3,531,905.4 |
| Water Area | 0.0 | 0.0 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Marengo, IN | Salem, IN | United States |
| Age 0 to 4 | 6.6% | 6.5% | 5.9% |
| Age 5 to 9 | 8.2% | 5.7% | 6.1% |
| Age 10 to 14 | 3.7% | 6.7% | 6.6% |
| Age 15 to 17 | 3.3% | 3.0% | 3.9% |
| Age 18 to 20 | 6.1% | 1.6% | 4.0% |
| Age 21 to 24 | 4.9% | 7.8% | 5.2% |
| Age 25 to 34 | 15.3% | 13.7% | 13.8% |
| Age 35 to 44 | 12.2% | 11.6% | 12.9% |
| Age 45 to 54 | 12.0% | 9.1% | 12.6% |
| Age 55 to 59 | 5.7% | 10.2% | 6.7% |
| Age 60 to 64 | 6.0% | 5.1% | 6.3% |
| Age 65 to 74 | 7.7% | 9.1% | 9.6% |
| Age 75 to 84 | 5.1% | 6.6% | 4.5% |
| Age 85 and over | 3.3% | 3.2% | 1.9% |
| space1 | | | |
| Race | | | |
| | Marengo, IN | Salem, IN | United States |
| White | 92.8% | 95.3% | 59.4% |
| Black | 0.0% | 0.0% | 12.2% |
| Asian | 0.0% | 0.1% | 5.6% |
| Native American | 0.0% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.0% | 0.4% |
| Two or More Races | 1.8% | 2.5% | 3.2% |
| Hispanic | 5.5% | 2.1% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Marengo, IN | Salem, IN | United States |
| Married Population | 50.4% | 41.6% | 49.8% |
| Currently Married | 49.6% | 40.2% | 48.0% |
| Married but Separated | 0.8% | 1.4% | 1.8% |
| Single Population | 49.6% | 58.4% | 50.2% |
| Never Married | 24.1% | 31.5% | 33.8% |
| Divorced | 17.4% | 18.5% | 10.8% |
| Widowed | 8.0% | 8.4% | 5.6% |
| space5 | | | |
| Household Size | 2.35 | 2.45 | 2.60 |
| Households | 311 | 2,485 | 124,010,992 |
| Family Households | 172 | 1,448 | 80,755,759 |
| Married couple, w/children | 19.8% | 27.6% | 30.5% |
| Married couple, no children | 59.9% | 39.4% | 42.9% |
| Non Family Households | 139 | 1,037 | 43,255,233 |
| Single householder, w/children | 16.9% | 22.2% | 15.8% |
| Single householder, no children | 3.5% | 10.8% | 10.8% |