| | Lewiston, UT | Roundup, MT | United States |
| Population | 2,043 | 1,708 | 329,725,481 |
| Female Population | 49.1% | 50.6% | 50.5% |
| Male Population | 51.0% | 49.4% | 49.5% |
| Median Age | 35.3 | 49.8 | 38.4 |
| space3 | | | |
| Population - 2010 | 1,779 | 1,789 | 309,327,143 |
| Population - 2000 | 1,877 | 1,931 | 285,036,114 |
| Population - 1990 | 1,532 | 1,808 | 251,960,433 |
| Pop. 2000 to Now | -5.2% | -3.5% | 15.6% |
| Pop. 1990 to Now | 16.2% | 3.1% | 30.8% |
| space4 | | | |
| Population Density | 80.3 | 1,321.0 | 93.4 |
| Land Area | 25.4 | 1.3 | 3,531,905.4 |
| Water Area | 0.1 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Lewiston, UT | Roundup, MT | United States |
| Age 0 to 4 | 7.3% | 2.8% | 5.9% |
| Age 5 to 9 | 7.1% | 4.7% | 6.1% |
| Age 10 to 14 | 8.9% | 8.4% | 6.6% |
| Age 15 to 17 | 7.9% | 4.5% | 3.9% |
| Age 18 to 20 | 3.6% | 4.9% | 4.0% |
| Age 21 to 24 | 3.9% | 2.9% | 5.2% |
| Age 25 to 34 | 10.6% | 8.0% | 13.8% |
| Age 35 to 44 | 11.7% | 10.0% | 12.9% |
| Age 45 to 54 | 14.7% | 11.0% | 12.6% |
| Age 55 to 59 | 4.8% | 6.5% | 6.7% |
| Age 60 to 64 | 6.3% | 12.1% | 6.3% |
| Age 65 to 74 | 8.0% | 13.3% | 9.6% |
| Age 75 to 84 | 2.7% | 9.4% | 4.5% |
| Age 85 and over | 2.7% | 1.5% | 1.9% |
| space1 | | | |
| Race | | | |
| | Lewiston, UT | Roundup, MT | United States |
| White | 91.0% | 90.7% | 59.4% |
| Black | 0.0% | 0.0% | 12.2% |
| Asian | 0.0% | 0.0% | 5.6% |
| Native American | 1.8% | 0.9% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.0% | 0.4% |
| Two or More Races | 1.9% | 2.1% | 3.2% |
| Hispanic | 5.3% | 6.3% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Lewiston, UT | Roundup, MT | United States |
| Married Population | 66.0% | 51.7% | 49.8% |
| Currently Married | 65.9% | 50.2% | 48.0% |
| Married but Separated | 0.1% | 1.5% | 1.8% |
| Single Population | 34.0% | 48.3% | 50.2% |
| Never Married | 22.2% | 22.1% | 33.8% |
| Divorced | 7.8% | 15.0% | 10.8% |
| Widowed | 4.0% | 11.3% | 5.6% |
| space5 | | | |
| Household Size | 3.04 | 2.03 | 2.60 |
| Households | 668 | 831 | 124,010,992 |
| Family Households | 593 | 413 | 80,755,759 |
| Married couple, w/children | 39.6% | 27.6% | 30.5% |
| Married couple, no children | 45.2% | 53.8% | 42.9% |
| Non Family Households | 75 | 418 | 43,255,233 |
| Single householder, w/children | 11.1% | 9.0% | 15.8% |
| Single householder, no children | 4.0% | 9.7% | 10.8% |