| | Erin, TN | Mountain City, TN | United States |
| Population | 1,607 | 2,367 | 329,725,481 |
| Female Population | 46.3% | 52.9% | 50.5% |
| Male Population | 53.7% | 47.1% | 49.5% |
| Median Age | 42.8 | 44.7 | 38.4 |
| space3 | | | |
| Population - 2010 | 1,349 | 2,514 | 309,327,143 |
| Population - 2000 | 1,490 | 2,383 | 285,036,114 |
| Population - 1990 | 1,586 | 2,169 | 251,960,433 |
| Pop. 2000 to Now | -12.2% | 2.6% | 15.6% |
| Pop. 1990 to Now | -17.5% | 12.7% | 30.8% |
| space4 | | | |
| Population Density | 412.5 | 702.4 | 93.4 |
| Land Area | 3.9 | 3.4 | 3,531,905.4 |
| Water Area | 0.0 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Erin, TN | Mountain City, TN | United States |
| Age 0 to 4 | 3.2% | 7.3% | 5.9% |
| Age 5 to 9 | 7.0% | 4.6% | 6.1% |
| Age 10 to 14 | 9.1% | 6.8% | 6.6% |
| Age 15 to 17 | 7.8% | 0.4% | 3.9% |
| Age 18 to 20 | 3.2% | 1.1% | 4.0% |
| Age 21 to 24 | 6.0% | 5.2% | 5.2% |
| Age 25 to 34 | 5.0% | 15.4% | 13.8% |
| Age 35 to 44 | 10.6% | 9.6% | 12.9% |
| Age 45 to 54 | 14.7% | 9.3% | 12.6% |
| Age 55 to 59 | 3.3% | 4.6% | 6.7% |
| Age 60 to 64 | 7.2% | 9.2% | 6.3% |
| Age 65 to 74 | 12.8% | 9.0% | 9.6% |
| Age 75 to 84 | 6.7% | 12.6% | 4.5% |
| Age 85 and over | 3.2% | 5.0% | 1.9% |
| space1 | | | |
| Race | | | |
| | Erin, TN | Mountain City, TN | United States |
| White | 90.7% | 84.8% | 59.4% |
| Black | 9.1% | 3.8% | 12.2% |
| Asian | 0.0% | 1.0% | 5.6% |
| Native American | 0.0% | 0.7% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.0% | 0.4% |
| Two or More Races | 0.2% | 2.6% | 3.2% |
| Hispanic | 0.0% | 7.1% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Erin, TN | Mountain City, TN | United States |
| Married Population | 35.1% | 42.5% | 49.8% |
| Currently Married | 33.4% | 39.1% | 48.0% |
| Married but Separated | 1.8% | 3.4% | 1.8% |
| Single Population | 64.9% | 57.5% | 50.2% |
| Never Married | 37.7% | 25.0% | 33.8% |
| Divorced | 18.8% | 20.2% | 10.8% |
| Widowed | 8.4% | 12.2% | 5.6% |
| space5 | | | |
| Household Size | 3.18 | 2.09 | 2.60 |
| Households | 459 | 1,022 | 124,010,992 |
| Family Households | 219 | 513 | 80,755,759 |
| Married couple, w/children | 27.9% | 18.9% | 30.5% |
| Married couple, no children | 62.6% | 46.2% | 42.9% |
| Non Family Households | 240 | 509 | 43,255,233 |
| Single householder, w/children | 5.0% | 24.6% | 15.8% |
| Single householder, no children | 4.6% | 10.3% | 10.8% |