| | Port Mansfield, TX | Port Isabel, TX | United States |
| Population | 132 | 5,208 | 329,725,481 |
| Female Population | 43.9% | 50.5% | 50.5% |
| Male Population | 56.1% | 49.5% | 49.5% |
| Median Age | 62.9 | 37.9 | 38.4 |
| space3 | | | |
| Population - 2010 | 307 | 6,314 | 309,327,143 |
| Population - 2000 | 415 | 4,865 | 285,036,114 |
| Population - 1990 | 231 | 4,467 | 251,960,433 |
| Pop. 2000 to Now | -77.8% | 28.0% | 15.6% |
| Pop. 1990 to Now | -60.2% | 39.4% | 30.8% |
| space4 | | | |
| Population Density | 26.7 | 776.9 | 93.4 |
| Land Area | 4.9 | 6.7 | 3,531,905.4 |
| Water Area | 1.4 | 7.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Port Mansfield, TX | Port Isabel, TX | United States |
| Age 0 to 4 | 6.8% | 6.4% | 5.9% |
| Age 5 to 9 | 0.0% | 8.2% | 6.1% |
| Age 10 to 14 | 0.0% | 10.0% | 6.6% |
| Age 15 to 17 | 0.0% | 3.4% | 3.9% |
| Age 18 to 20 | 0.0% | 2.0% | 4.0% |
| Age 21 to 24 | 0.0% | 2.3% | 5.2% |
| Age 25 to 34 | 6.8% | 13.0% | 13.8% |
| Age 35 to 44 | 10.6% | 13.0% | 12.9% |
| Age 45 to 54 | 20.5% | 8.9% | 12.6% |
| Age 55 to 59 | 0.0% | 7.0% | 6.7% |
| Age 60 to 64 | 9.8% | 7.5% | 6.3% |
| Age 65 to 74 | 31.1% | 10.0% | 9.6% |
| Age 75 to 84 | 11.4% | 6.5% | 4.5% |
| Age 85 and over | 3.0% | 1.8% | 1.9% |
| space1 | | | |
| Race | | | |
| | Port Mansfield, TX | Port Isabel, TX | United States |
| White | 78.8% | 14.7% | 59.4% |
| Black | 0.0% | 0.0% | 12.2% |
| Asian | 0.0% | 1.4% | 5.6% |
| Native American | 0.0% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 1.7% | 0.4% |
| Two or More Races | 0.0% | 0.3% | 3.2% |
| Hispanic | 21.2% | 82.0% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Port Mansfield, TX | Port Isabel, TX | United States |
| Married Population | 49.6% | 58.3% | 49.8% |
| Currently Married | 49.6% | 53.9% | 48.0% |
| Married but Separated | 0.0% | 4.4% | 1.8% |
| Single Population | 50.4% | 41.7% | 50.2% |
| Never Married | 22.0% | 25.7% | 33.8% |
| Divorced | 6.5% | 9.4% | 10.8% |
| Widowed | 22.0% | 6.7% | 5.6% |
| space5 | | | |
| Household Size | 1.89 | 2.87 | 2.60 |
| Households | 70 | 1,817 | 124,010,992 |
| Family Households | 31 | 1,254 | 80,755,759 |
| Married couple, w/children | 0.0% | 28.4% | 30.5% |
| Married couple, no children | 100.0% | 35.9% | 42.9% |
| Non Family Households | 39 | 563 | 43,255,233 |
| Single householder, w/children | 0.0% | 25.4% | 15.8% |
| Single householder, no children | 0.0% | 10.4% | 10.8% |