| | Tiffin, IA | Keokuk, IA | United States |
| Population | 4,482 | 9,977 | 329,725,481 |
| Female Population | 51.1% | 53.0% | 50.5% |
| Male Population | 48.9% | 47.0% | 49.5% |
| Median Age | 32.3 | 40.2 | 38.4 |
| space3 | | | |
| Population - 2010 | 1,968 | 10,770 | 309,327,143 |
| Population - 2000 | 975 | 11,427 | 285,036,114 |
| Population - 1990 | 460 | 12,451 | 251,960,433 |
| Pop. 2000 to Now | 374.8% | -11.7% | 15.6% |
| Pop. 1990 to Now | 906.3% | -19.0% | 30.8% |
| space4 | | | |
| Population Density | 1,093.7 | 1,098.9 | 93.4 |
| Land Area | 4.1 | 9.1 | 3,531,905.4 |
| Water Area | 0.0 | 1.4 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Tiffin, IA | Keokuk, IA | United States |
| Age 0 to 4 | 9.5% | 6.5% | 5.9% |
| Age 5 to 9 | 7.8% | 5.9% | 6.1% |
| Age 10 to 14 | 7.6% | 7.0% | 6.6% |
| Age 15 to 17 | 2.2% | 2.7% | 3.9% |
| Age 18 to 20 | 3.0% | 2.9% | 4.0% |
| Age 21 to 24 | 7.3% | 4.7% | 5.2% |
| Age 25 to 34 | 23.3% | 14.8% | 13.8% |
| Age 35 to 44 | 9.5% | 11.4% | 12.9% |
| Age 45 to 54 | 9.4% | 9.7% | 12.6% |
| Age 55 to 59 | 7.3% | 6.0% | 6.7% |
| Age 60 to 64 | 3.0% | 8.1% | 6.3% |
| Age 65 to 74 | 7.4% | 12.4% | 9.6% |
| Age 75 to 84 | 1.3% | 5.3% | 4.5% |
| Age 85 and over | 1.5% | 2.6% | 1.9% |
| space1 | | | |
| Race | | | |
| | Tiffin, IA | Keokuk, IA | United States |
| White | 78.0% | 87.3% | 59.4% |
| Black | 1.5% | 4.1% | 12.2% |
| Asian | 2.3% | 1.0% | 5.6% |
| Native American | 0.8% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 1.5% | 0.0% | 0.4% |
| Two or More Races | 7.2% | 2.8% | 3.2% |
| Hispanic | 8.7% | 4.8% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Tiffin, IA | Keokuk, IA | United States |
| Married Population | 55.2% | 43.5% | 49.8% |
| Currently Married | 53.7% | 42.0% | 48.0% |
| Married but Separated | 1.5% | 1.4% | 1.8% |
| Single Population | 44.8% | 56.5% | 50.2% |
| Never Married | 28.3% | 33.9% | 33.8% |
| Divorced | 14.8% | 15.8% | 10.8% |
| Widowed | 1.7% | 6.9% | 5.6% |
| space5 | | | |
| Household Size | 2.55 | 2.24 | 2.60 |
| Households | 1,755 | 4,386 | 124,010,992 |
| Family Households | 1,319 | 2,507 | 80,755,759 |
| Married couple, w/children | 33.3% | 21.8% | 30.5% |
| Married couple, no children | 35.6% | 44.0% | 42.9% |
| Non Family Households | 436 | 1,879 | 43,255,233 |
| Single householder, w/children | 18.0% | 25.5% | 15.8% |
| Single householder, no children | 13.0% | 8.7% | 10.8% |