| | Marshalltown, IA | Bettendorf, IA | United States |
| Population | 27,570 | 38,631 | 329,725,481 |
| Female Population | 49.6% | 52.0% | 50.5% |
| Male Population | 50.4% | 48.0% | 49.5% |
| Median Age | 36 | 38.9 | 38.4 |
| space3 | | | |
| Population - 2010 | 27,605 | 33,281 | 309,327,143 |
| Population - 2000 | 26,009 | 31,275 | 285,036,114 |
| Population - 1990 | 25,178 | 28,132 | 251,960,433 |
| Pop. 2000 to Now | 2.8% | 17.2% | 15.6% |
| Pop. 1990 to Now | 6.2% | 30.3% | 30.8% |
| space4 | | | |
| Population Density | 1,429.9 | 1,813.9 | 93.4 |
| Land Area | 19.3 | 21.3 | 3,531,905.4 |
| Water Area | 0.0 | 1.1 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Marshalltown, IA | Bettendorf, IA | United States |
| Age 0 to 4 | 7.1% | 6.2% | 5.9% |
| Age 5 to 9 | 7.1% | 8.0% | 6.1% |
| Age 10 to 14 | 8.2% | 7.3% | 6.6% |
| Age 15 to 17 | 4.1% | 4.5% | 3.9% |
| Age 18 to 20 | 3.7% | 3.7% | 4.0% |
| Age 21 to 24 | 6.1% | 2.6% | 5.2% |
| Age 25 to 34 | 12.0% | 11.7% | 13.8% |
| Age 35 to 44 | 11.9% | 14.3% | 12.9% |
| Age 45 to 54 | 11.0% | 13.0% | 12.6% |
| Age 55 to 59 | 6.2% | 5.7% | 6.7% |
| Age 60 to 64 | 5.3% | 6.0% | 6.3% |
| Age 65 to 74 | 9.7% | 10.0% | 9.6% |
| Age 75 to 84 | 4.8% | 5.6% | 4.5% |
| Age 85 and over | 2.9% | 1.4% | 1.9% |
| space1 | | | |
| Race | | | |
| | Marshalltown, IA | Bettendorf, IA | United States |
| White | 57.9% | 83.5% | 59.4% |
| Black | 1.4% | 1.8% | 12.2% |
| Asian | 4.7% | 6.4% | 5.6% |
| Native American | 0.3% | 0.1% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.2% | 0.2% | 0.4% |
| Two or More Races | 3.3% | 3.5% | 3.2% |
| Hispanic | 32.3% | 4.6% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Marshalltown, IA | Bettendorf, IA | United States |
| Married Population | 52.1% | 56.6% | 49.8% |
| Currently Married | 50.8% | 55.4% | 48.0% |
| Married but Separated | 1.2% | 1.3% | 1.8% |
| Single Population | 47.9% | 43.4% | 50.2% |
| Never Married | 31.4% | 25.4% | 33.8% |
| Divorced | 10.6% | 12.9% | 10.8% |
| Widowed | 5.9% | 5.1% | 5.6% |
| space5 | | | |
| Household Size | 2.62 | 2.51 | 2.60 |
| Households | 10,098 | 15,311 | 124,010,992 |
| Family Households | 6,522 | 10,374 | 80,755,759 |
| Married couple, w/children | 37.3% | 38.6% | 30.5% |
| Married couple, no children | 39.7% | 41.1% | 42.9% |
| Non Family Households | 3,576 | 4,937 | 43,255,233 |
| Single householder, w/children | 18.6% | 15.0% | 15.8% |
| Single householder, no children | 4.4% | 5.4% | 10.8% |