| | Opelousas, LA | Marshall, TX | United States |
| Population | 15,884 | 22,862 | 329,725,481 |
| Female Population | 52.6% | 52.8% | 50.5% |
| Male Population | 47.4% | 47.2% | 49.5% |
| Median Age | 34.5 | 34.7 | 38.4 |
| space3 | | | |
| Population - 2010 | 16,658 | 23,528 | 309,327,143 |
| Population - 2000 | 22,860 | 23,935 | 285,036,114 |
| Population - 1990 | 18,151 | 23,682 | 251,960,433 |
| Pop. 2000 to Now | -31.9% | -5.9% | 15.6% |
| Pop. 1990 to Now | -14.3% | -4.9% | 30.8% |
| space4 | | | |
| Population Density | 2,003.8 | 772.5 | 93.4 |
| Land Area | 7.9 | 29.6 | 3,531,905.4 |
| Water Area | 0.0 | 0.1 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Opelousas, LA | Marshall, TX | United States |
| Age 0 to 4 | 6.2% | 6.8% | 5.9% |
| Age 5 to 9 | 9.6% | 6.1% | 6.1% |
| Age 10 to 14 | 9.4% | 7.9% | 6.6% |
| Age 15 to 17 | 4.0% | 4.7% | 3.9% |
| Age 18 to 20 | 4.9% | 5.8% | 4.0% |
| Age 21 to 24 | 3.6% | 4.9% | 5.2% |
| Age 25 to 34 | 13.1% | 14.4% | 13.8% |
| Age 35 to 44 | 11.8% | 13.2% | 12.9% |
| Age 45 to 54 | 11.4% | 9.2% | 12.6% |
| Age 55 to 59 | 5.3% | 5.6% | 6.7% |
| Age 60 to 64 | 6.3% | 5.1% | 6.3% |
| Age 65 to 74 | 8.2% | 10.4% | 9.6% |
| Age 75 to 84 | 4.2% | 3.9% | 4.5% |
| Age 85 and over | 2.0% | 1.9% | 1.9% |
| space1 | | | |
| Race | | | |
| | Opelousas, LA | Marshall, TX | United States |
| White | 20.5% | 35.7% | 59.4% |
| Black | 75.0% | 37.8% | 12.2% |
| Asian | 0.0% | 1.2% | 5.6% |
| Native American | 0.1% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.9% | 0.0% | 0.4% |
| Two or More Races | 1.5% | 2.8% | 3.2% |
| Hispanic | 2.1% | 22.5% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Opelousas, LA | Marshall, TX | United States |
| Married Population | 30.3% | 37.7% | 49.8% |
| Currently Married | 26.5% | 35.8% | 48.0% |
| Married but Separated | 3.8% | 1.9% | 1.8% |
| Single Population | 69.7% | 62.3% | 50.2% |
| Never Married | 48.9% | 41.8% | 33.8% |
| Divorced | 11.5% | 13.1% | 10.8% |
| Widowed | 9.3% | 7.5% | 5.6% |
| space5 | | | |
| Household Size | 2.74 | 2.70 | 2.60 |
| Households | 5,599 | 7,996 | 124,010,992 |
| Family Households | 3,435 | 5,113 | 80,755,759 |
| Married couple, w/children | 22.8% | 24.9% | 30.5% |
| Married couple, no children | 19.6% | 32.6% | 42.9% |
| Non Family Households | 2,164 | 2,883 | 43,255,233 |
| Single householder, w/children | 34.4% | 26.2% | 15.8% |
| Single householder, no children | 23.2% | 16.4% | 10.8% |