| | Gretna, NE | Altoona, IA | United States |
| Population | 5,106 | 19,345 | 329,725,481 |
| Female Population | 52.7% | 51.8% | 50.5% |
| Male Population | 47.3% | 48.2% | 49.5% |
| Median Age | 36.2 | 36.2 | 38.4 |
| space3 | | | |
| Population - 2010 | 4,936 | 14,703 | 309,327,143 |
| Population - 2000 | 2,355 | 10,345 | 285,036,114 |
| Population - 1990 | 2,249 | 7,191 | 251,960,433 |
| Pop. 2000 to Now | 113.3% | 88.5% | 15.6% |
| Pop. 1990 to Now | 123.4% | 171.2% | 30.8% |
| space4 | | | |
| Population Density | 2,097.8 | 1,788.2 | 93.4 |
| Land Area | 2.4 | 10.8 | 3,531,905.4 |
| Water Area | 0.0 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Gretna, NE | Altoona, IA | United States |
| Age 0 to 4 | 5.4% | 6.2% | 5.9% |
| Age 5 to 9 | 9.6% | 8.9% | 6.1% |
| Age 10 to 14 | 5.9% | 7.4% | 6.6% |
| Age 15 to 17 | 6.0% | 4.5% | 3.9% |
| Age 18 to 20 | 4.0% | 2.6% | 4.0% |
| Age 21 to 24 | 3.9% | 4.5% | 5.2% |
| Age 25 to 34 | 14.4% | 14.3% | 13.8% |
| Age 35 to 44 | 16.4% | 16.1% | 12.9% |
| Age 45 to 54 | 12.4% | 11.6% | 12.6% |
| Age 55 to 59 | 5.9% | 5.5% | 6.7% |
| Age 60 to 64 | 5.2% | 5.4% | 6.3% |
| Age 65 to 74 | 5.0% | 7.4% | 9.6% |
| Age 75 to 84 | 4.0% | 4.0% | 4.5% |
| Age 85 and over | 1.9% | 1.5% | 1.9% |
| space1 | | | |
| Race | | | |
| | Gretna, NE | Altoona, IA | United States |
| White | 93.1% | 88.5% | 59.4% |
| Black | 0.4% | 3.2% | 12.2% |
| Asian | 0.0% | 0.6% | 5.6% |
| Native American | 0.0% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 1.0% | 0.2% |
| Other | 0.0% | 0.0% | 0.4% |
| Two or More Races | 0.8% | 1.9% | 3.2% |
| Hispanic | 5.8% | 4.7% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Gretna, NE | Altoona, IA | United States |
| Married Population | 49.1% | 53.9% | 49.8% |
| Currently Married | 47.9% | 53.4% | 48.0% |
| Married but Separated | 1.2% | 0.5% | 1.8% |
| Single Population | 50.9% | 46.1% | 50.2% |
| Never Married | 32.6% | 28.5% | 33.8% |
| Divorced | 10.8% | 14.1% | 10.8% |
| Widowed | 7.5% | 3.5% | 5.6% |
| space5 | | | |
| Household Size | 2.56 | 2.69 | 2.60 |
| Households | 1,980 | 7,159 | 124,010,992 |
| Family Households | 1,357 | 5,017 | 80,755,759 |
| Married couple, w/children | 33.0% | 35.1% | 30.5% |
| Married couple, no children | 36.3% | 41.0% | 42.9% |
| Non Family Households | 623 | 2,142 | 43,255,233 |
| Single householder, w/children | 22.1% | 17.5% | 15.8% |
| Single householder, no children | 8.6% | 6.3% | 10.8% |