| | Wellsburg, IA | Marshalltown, IA | United States |
| Population | 755 | 27,570 | 329,725,481 |
| Female Population | 54.3% | 49.6% | 50.5% |
| Male Population | 45.7% | 50.4% | 49.5% |
| Median Age | 49.1 | 36 | 38.4 |
| space3 | | | |
| Population - 2010 | 708 | 27,605 | 309,327,143 |
| Population - 2000 | 716 | 26,009 | 285,036,114 |
| Population - 1990 | 682 | 25,178 | 251,960,433 |
| Pop. 2000 to Now | -4.3% | 2.8% | 15.6% |
| Pop. 1990 to Now | 0.4% | 6.2% | 30.8% |
| space4 | | | |
| Population Density | 691.4 | 1,429.9 | 93.4 |
| Land Area | 1.1 | 19.3 | 3,531,905.4 |
| Water Area | 0.0 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Wellsburg, IA | Marshalltown, IA | United States |
| Age 0 to 4 | 4.9% | 7.1% | 5.9% |
| Age 5 to 9 | 4.8% | 7.1% | 6.1% |
| Age 10 to 14 | 5.2% | 8.2% | 6.6% |
| Age 15 to 17 | 3.6% | 4.1% | 3.9% |
| Age 18 to 20 | 1.1% | 3.7% | 4.0% |
| Age 21 to 24 | 1.9% | 6.1% | 5.2% |
| Age 25 to 34 | 13.8% | 12.0% | 13.8% |
| Age 35 to 44 | 7.6% | 11.9% | 12.9% |
| Age 45 to 54 | 17.4% | 11.0% | 12.6% |
| Age 55 to 59 | 6.6% | 6.2% | 6.7% |
| Age 60 to 64 | 6.0% | 5.3% | 6.3% |
| Age 65 to 74 | 13.6% | 9.7% | 9.6% |
| Age 75 to 84 | 8.6% | 4.8% | 4.5% |
| Age 85 and over | 5.2% | 2.9% | 1.9% |
| space1 | | | |
| Race | | | |
| | Wellsburg, IA | Marshalltown, IA | United States |
| White | 97.0% | 57.9% | 59.4% |
| Black | 1.1% | 1.4% | 12.2% |
| Asian | 0.3% | 4.7% | 5.6% |
| Native American | 0.0% | 0.3% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.2% | 0.4% |
| Two or More Races | 1.5% | 3.3% | 3.2% |
| Hispanic | 0.3% | 32.3% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Wellsburg, IA | Marshalltown, IA | United States |
| Married Population | 64.7% | 52.1% | 49.8% |
| Currently Married | 63.5% | 50.8% | 48.0% |
| Married but Separated | 1.2% | 1.2% | 1.8% |
| Single Population | 35.3% | 47.9% | 50.2% |
| Never Married | 17.6% | 31.4% | 33.8% |
| Divorced | 7.0% | 10.6% | 10.8% |
| Widowed | 10.7% | 5.9% | 5.6% |
| space5 | | | |
| Household Size | 2.19 | 2.62 | 2.60 |
| Households | 344 | 10,098 | 124,010,992 |
| Family Households | 213 | 6,522 | 80,755,759 |
| Married couple, w/children | 23.0% | 37.3% | 30.5% |
| Married couple, no children | 63.9% | 39.7% | 42.9% |
| Non Family Households | 131 | 3,576 | 43,255,233 |
| Single householder, w/children | 8.9% | 18.6% | 15.8% |
| Single householder, no children | 4.2% | 4.4% | 10.8% |