| | Promise City, IA | Corydon, IA | United States |
| Population | 97 | 1,749 | 329,725,481 |
| Female Population | 61.9% | 52.7% | 50.5% |
| Male Population | 38.1% | 47.3% | 49.5% |
| Median Age | 55.6 | 36.3 | 38.4 |
| space3 | | | |
| Population - 2010 | 109 | 1,591 | 309,327,143 |
| Population - 2000 | 105 | 1,591 | 285,036,114 |
| Population - 1990 | 132 | 1,675 | 251,960,433 |
| Pop. 2000 to Now | 4.8% | 0.1% | 15.6% |
| Pop. 1990 to Now | -16.7% | -4.9% | 30.8% |
| space4 | | | |
| Population Density | 513.2 | 1,255.6 | 93.4 |
| Land Area | 0.2 | 1.4 | 3,531,905.4 |
| Water Area | 0.0 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Promise City, IA | Corydon, IA | United States |
| Age 0 to 4 | 0.0% | 7.3% | 5.9% |
| Age 5 to 9 | 6.2% | 7.5% | 6.1% |
| Age 10 to 14 | 6.2% | 7.9% | 6.6% |
| Age 15 to 17 | 0.0% | 3.8% | 3.9% |
| Age 18 to 20 | 0.0% | 3.4% | 4.0% |
| Age 21 to 24 | 0.0% | 1.9% | 5.2% |
| Age 25 to 34 | 7.2% | 16.9% | 13.8% |
| Age 35 to 44 | 0.0% | 8.7% | 12.9% |
| Age 45 to 54 | 25.8% | 10.5% | 12.6% |
| Age 55 to 59 | 32.0% | 7.5% | 6.7% |
| Age 60 to 64 | 0.0% | 5.0% | 6.3% |
| Age 65 to 74 | 9.3% | 8.7% | 9.6% |
| Age 75 to 84 | 11.3% | 6.9% | 4.5% |
| Age 85 and over | 2.1% | 3.9% | 1.9% |
| space1 | | | |
| Race | | | |
| | Promise City, IA | Corydon, IA | United States |
| White | 94.8% | 90.3% | 59.4% |
| Black | 0.0% | 1.3% | 12.2% |
| Asian | 0.0% | 0.2% | 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 | 5.2% | 3.1% | 3.2% |
| Hispanic | 0.0% | 5.1% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Promise City, IA | Corydon, IA | United States |
| Married Population | 55.3% | 48.4% | 49.8% |
| Currently Married | 49.4% | 46.4% | 48.0% |
| Married but Separated | 5.9% | 2.1% | 1.8% |
| Single Population | 44.7% | 51.6% | 50.2% |
| Never Married | 10.6% | 21.4% | 33.8% |
| Divorced | 24.7% | 19.0% | 10.8% |
| Widowed | 9.4% | 11.2% | 5.6% |
| space5 | | | |
| Household Size | 1.98 | 2.44 | 2.60 |
| Households | 49 | 679 | 124,010,992 |
| Family Households | 24 | 423 | 80,755,759 |
| Married couple, w/children | 29.2% | 30.3% | 30.5% |
| Married couple, no children | 41.7% | 39.0% | 42.9% |
| Non Family Households | 25 | 256 | 43,255,233 |
| Single householder, w/children | 16.7% | 25.3% | 15.8% |
| Single householder, no children | 12.5% | 5.4% | 10.8% |