| | Denver, SD | Madison, SD | United States |
| Population | 293 | 6,388 | 329,725,481 |
| Female Population | 51.5% | 48.6% | 50.5% |
| Male Population | 48.5% | 51.4% | 49.5% |
| Median Age | 34.8 | 36.2 | 38.4 |
| space3 | | | |
| Population - 2010 | 195 | 6,533 | 309,327,143 |
| Population - 2000 | 250 | 6,540 | 285,036,114 |
| Population - 1990 | 245 | 6,257 | 251,960,433 |
| Pop. 2000 to Now | -22.4% | 8.0% | 15.6% |
| Pop. 1990 to Now | -20.8% | 12.9% | 30.8% |
| space4 | | | |
| Population Density | 4.5 | 1,383.9 | 93.4 |
| Land Area | 65.2 | 4.6 | 3,531,905.4 |
| Water Area | 1.1 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Denver, SD | Madison, SD | United States |
| Age 0 to 4 | 0.0% | 6.4% | 5.9% |
| Age 5 to 9 | 19.5% | 6.2% | 6.1% |
| Age 10 to 14 | 13.3% | 5.9% | 6.6% |
| Age 15 to 17 | 6.5% | 2.6% | 3.9% |
| Age 18 to 20 | 5.1% | 8.5% | 4.0% |
| Age 21 to 24 | 1.7% | 7.8% | 5.2% |
| Age 25 to 34 | 4.8% | 12.0% | 13.8% |
| Age 35 to 44 | 22.2% | 8.7% | 12.9% |
| Age 45 to 54 | 6.1% | 6.5% | 12.6% |
| Age 55 to 59 | 4.1% | 8.4% | 6.7% |
| Age 60 to 64 | 6.8% | 7.9% | 6.3% |
| Age 65 to 74 | 7.9% | 10.9% | 9.6% |
| Age 75 to 84 | 2.0% | 4.5% | 4.5% |
| Age 85 and over | 0.0% | 3.7% | 1.9% |
| space1 | | | |
| Race | | | |
| | Denver, SD | Madison, SD | United States |
| White | 100.0% | 91.2% | 59.4% |
| Black | 0.0% | 0.2% | 12.2% |
| Asian | 0.0% | 0.0% | 5.6% |
| Native American | 0.0% | 2.2% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.1% | 0.2% |
| Other | 0.0% | 0.0% | 0.4% |
| Two or More Races | 0.0% | 3.0% | 3.2% |
| Hispanic | 0.0% | 3.4% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Denver, SD | Madison, SD | United States |
| Married Population | 65.0% | 45.9% | 49.8% |
| Currently Married | 65.0% | 42.5% | 48.0% |
| Married but Separated | 0.0% | 3.4% | 1.8% |
| Single Population | 35.0% | 54.1% | 50.2% |
| Never Married | 29.9% | 37.6% | 33.8% |
| Divorced | 2.5% | 10.2% | 10.8% |
| Widowed | 2.5% | 6.2% | 5.6% |
| space5 | | | |
| Household Size | 3.86 | 2.40 | 2.60 |
| Households | 76 | 2,430 | 124,010,992 |
| Family Households | 68 | 1,386 | 80,755,759 |
| Married couple, w/children | 54.4% | 27.9% | 30.5% |
| Married couple, no children | 38.2% | 49.6% | 42.9% |
| Non Family Households | 8 | 1,044 | 43,255,233 |
| Single householder, w/children | 0.0% | 14.1% | 15.8% |
| Single householder, no children | 7.4% | 8.4% | 10.8% |