| | Cotter, IA | Belle Plaine, IA | United States |
| Population | 24 | 2,419 | 329,725,481 |
| Female Population | 50.0% | 45.0% | 50.5% |
| Male Population | 50.0% | 55.0% | 49.5% |
| Median Age | 52.5 | 44.1 | 38.4 |
| space3 | | | |
| Population - 2010 | 44 | 2,532 | 309,327,143 |
| Population - 2000 | 48 | 2,878 | 285,036,114 |
| Population - 1990 | 53 | 2,834 | 251,960,433 |
| Pop. 2000 to Now | -12.5% | -16.0% | 15.6% |
| Pop. 1990 to Now | -20.8% | -14.7% | 30.8% |
| space4 | | | |
| Population Density | 98.0 | 760.9 | 93.4 |
| Land Area | 0.2 | 3.2 | 3,531,905.4 |
| Water Area | 0.0 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Cotter, IA | Belle Plaine, IA | United States |
| Age 0 to 4 | 4.2% | 6.3% | 5.9% |
| Age 5 to 9 | 4.2% | 4.3% | 6.1% |
| Age 10 to 14 | 8.3% | 4.9% | 6.6% |
| Age 15 to 17 | 4.2% | 4.9% | 3.9% |
| Age 18 to 20 | 0.0% | 3.3% | 4.0% |
| Age 21 to 24 | 0.0% | 4.2% | 5.2% |
| Age 25 to 34 | 8.3% | 11.5% | 13.8% |
| Age 35 to 44 | 12.5% | 13.9% | 12.9% |
| Age 45 to 54 | 20.8% | 11.9% | 12.6% |
| Age 55 to 59 | 4.2% | 6.9% | 6.7% |
| Age 60 to 64 | 8.3% | 4.4% | 6.3% |
| Age 65 to 74 | 16.7% | 14.8% | 9.6% |
| Age 75 to 84 | 8.3% | 5.5% | 4.5% |
| Age 85 and over | 0.0% | 3.2% | 1.9% |
| space1 | | | |
| Race | | | |
| | Cotter, IA | Belle Plaine, IA | United States |
| White | 83.3% | 93.4% | 59.4% |
| Black | 0.0% | 0.0% | 12.2% |
| Asian | 0.0% | 0.0% | 5.6% |
| Native American | 0.0% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 2.0% | 0.4% |
| Two or More Races | 0.0% | 1.9% | 3.2% |
| Hispanic | 16.7% | 2.6% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Cotter, IA | Belle Plaine, IA | United States |
| Married Population | 60.0% | 49.7% | 49.8% |
| Currently Married | 60.0% | 46.4% | 48.0% |
| Married but Separated | 0.0% | 3.2% | 1.8% |
| Single Population | 40.0% | 50.3% | 50.2% |
| Never Married | 35.0% | 27.6% | 33.8% |
| Divorced | 0.0% | 15.8% | 10.8% |
| Widowed | 5.0% | 7.0% | 5.6% |
| space5 | | | |
| Household Size | 2.18 | 2.35 | 2.60 |
| Households | 11 | 1,011 | 124,010,992 |
| Family Households | 7 | 611 | 80,755,759 |
| Married couple, w/children | 14.3% | 20.5% | 30.5% |
| Married couple, no children | 71.4% | 53.5% | 42.9% |
| Non Family Households | 4 | 400 | 43,255,233 |
| Single householder, w/children | 14.3% | 20.9% | 15.8% |
| Single householder, no children | 0.0% | 5.1% | 10.8% |