| | Niagara, WI | Iron Mountain, MI | United States |
| Population | 1,420 | 7,516 | 329,725,481 |
| Female Population | 53.8% | 46.4% | 50.5% |
| Male Population | 46.2% | 53.6% | 49.5% |
| Median Age | 47.8 | 43.2 | 38.4 |
| space3 | | | |
| Population - 2010 | 1,624 | 7,630 | 309,327,143 |
| Population - 2000 | 1,880 | 8,154 | 285,036,114 |
| Population - 1990 | 1,999 | 8,525 | 251,960,433 |
| Pop. 2000 to Now | -18.4% | -10.9% | 15.6% |
| Pop. 1990 to Now | -23.2% | -14.7% | 30.8% |
| space4 | | | |
| Population Density | 514.1 | 996.3 | 93.4 |
| Land Area | 2.8 | 7.5 | 3,531,905.4 |
| Water Area | 0.2 | 0.7 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Niagara, WI | Iron Mountain, MI | United States |
| Age 0 to 4 | 2.7% | 5.1% | 5.9% |
| Age 5 to 9 | 5.5% | 6.4% | 6.1% |
| Age 10 to 14 | 6.1% | 5.1% | 6.6% |
| Age 15 to 17 | 3.7% | 2.9% | 3.9% |
| Age 18 to 20 | 1.6% | 3.2% | 4.0% |
| Age 21 to 24 | 5.6% | 2.8% | 5.2% |
| Age 25 to 34 | 11.2% | 13.2% | 13.8% |
| Age 35 to 44 | 7.9% | 12.7% | 12.9% |
| Age 45 to 54 | 14.7% | 13.0% | 12.6% |
| Age 55 to 59 | 9.4% | 8.1% | 6.7% |
| Age 60 to 64 | 10.5% | 7.9% | 6.3% |
| Age 65 to 74 | 10.0% | 11.1% | 9.6% |
| Age 75 to 84 | 7.8% | 4.7% | 4.5% |
| Age 85 and over | 3.1% | 3.8% | 1.9% |
| space1 | | | |
| Race | | | |
| | Niagara, WI | Iron Mountain, MI | United States |
| White | 94.9% | 93.1% | 59.4% |
| Black | 0.4% | 1.5% | 12.2% |
| Asian | 0.0% | 0.8% | 5.6% |
| Native American | 0.0% | 1.6% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.3% | 0.4% |
| Two or More Races | 3.9% | 0.9% | 3.2% |
| Hispanic | 0.8% | 1.9% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Niagara, WI | Iron Mountain, MI | United States |
| Married Population | 52.1% | 50.8% | 49.8% |
| Currently Married | 50.7% | 48.7% | 48.0% |
| Married but Separated | 1.4% | 2.2% | 1.8% |
| Single Population | 47.9% | 49.2% | 50.2% |
| Never Married | 24.6% | 28.7% | 33.8% |
| Divorced | 16.6% | 15.9% | 10.8% |
| Widowed | 6.7% | 4.5% | 5.6% |
| space5 | | | |
| Household Size | 2.20 | 2.23 | 2.60 |
| Households | 644 | 3,296 | 124,010,992 |
| Family Households | 398 | 2,009 | 80,755,759 |
| Married couple, w/children | 16.1% | 20.9% | 30.5% |
| Married couple, no children | 58.0% | 53.4% | 42.9% |
| Non Family Households | 246 | 1,287 | 43,255,233 |
| Single householder, w/children | 18.8% | 15.4% | 15.8% |
| Single householder, no children | 7.0% | 10.4% | 10.8% |