| | Griffith, IN | Portage, IN | United States |
| Population | 16,213 | 37,540 | 329,725,481 |
| Female Population | 50.6% | 51.5% | 50.5% |
| Male Population | 49.4% | 48.6% | 49.5% |
| Median Age | 37.8 | 37.1 | 38.4 |
| space3 | | | |
| Population - 2010 | 16,909 | 36,853 | 309,327,143 |
| Population - 2000 | 17,334 | 33,496 | 285,036,114 |
| Population - 1990 | 17,916 | 29,060 | 251,960,433 |
| Pop. 2000 to Now | -7.5% | 10.9% | 15.6% |
| Pop. 1990 to Now | -10.5% | 27.8% | 30.8% |
| space4 | | | |
| Population Density | 2,096.1 | 1,470.0 | 93.4 |
| Land Area | 7.7 | 25.5 | 3,531,905.4 |
| Water Area | 0.0 | 2.1 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Griffith, IN | Portage, IN | United States |
| Age 0 to 4 | 6.1% | 5.6% | 5.9% |
| Age 5 to 9 | 4.9% | 6.2% | 6.1% |
| Age 10 to 14 | 3.2% | 7.2% | 6.6% |
| Age 15 to 17 | 4.3% | 3.4% | 3.9% |
| Age 18 to 20 | 4.9% | 3.7% | 4.0% |
| Age 21 to 24 | 5.7% | 5.8% | 5.2% |
| Age 25 to 34 | 15.1% | 15.0% | 13.8% |
| Age 35 to 44 | 14.8% | 11.9% | 12.9% |
| Age 45 to 54 | 14.1% | 12.5% | 12.6% |
| Age 55 to 59 | 6.8% | 7.5% | 6.7% |
| Age 60 to 64 | 6.0% | 7.2% | 6.3% |
| Age 65 to 74 | 9.5% | 9.4% | 9.6% |
| Age 75 to 84 | 3.5% | 3.6% | 4.5% |
| Age 85 and over | 1.1% | 0.9% | 1.9% |
| space1 | | | |
| Race | | | |
| | Griffith, IN | Portage, IN | United States |
| White | 63.2% | 67.0% | 59.4% |
| Black | 17.3% | 8.6% | 12.2% |
| Asian | 2.2% | 1.4% | 5.6% |
| Native American | 0.1% | 0.1% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.2% | 0.4% |
| Two or More Races | 2.3% | 2.1% | 3.2% |
| Hispanic | 14.9% | 20.6% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Griffith, IN | Portage, IN | United States |
| Married Population | 45.4% | 48.1% | 49.8% |
| Currently Married | 44.6% | 46.5% | 48.0% |
| Married but Separated | 0.8% | 1.6% | 1.8% |
| Single Population | 54.6% | 51.9% | 50.2% |
| Never Married | 35.7% | 32.6% | 33.8% |
| Divorced | 13.3% | 13.5% | 10.8% |
| Widowed | 5.6% | 5.8% | 5.6% |
| space5 | | | |
| Household Size | 2.42 | 2.54 | 2.60 |
| Households | 6,694 | 14,686 | 124,010,992 |
| Family Households | 4,544 | 9,757 | 80,755,759 |
| Married couple, w/children | 29.1% | 29.5% | 30.5% |
| Married couple, no children | 36.7% | 39.0% | 42.9% |
| Non Family Households | 2,150 | 4,929 | 43,255,233 |
| Single householder, w/children | 17.7% | 22.0% | 15.8% |
| Single householder, no children | 16.5% | 9.5% | 10.8% |