| | Firth, ID | Lyman, WY | United States |
| Population | 554 | 1,729 | 329,725,481 |
| Female Population | 46.2% | 48.8% | 50.5% |
| Male Population | 53.8% | 51.2% | 49.5% |
| Median Age | 35.2 | 34.8 | 38.4 |
| space3 | | | |
| Population - 2010 | 480 | 2,107 | 309,327,143 |
| Population - 2000 | 408 | 1,938 | 285,036,114 |
| Population - 1990 | 429 | 1,896 | 251,960,433 |
| Pop. 2000 to Now | 22.8% | 7.5% | 15.6% |
| Pop. 1990 to Now | 16.8% | 9.9% | 30.8% |
| space4 | | | |
| Population Density | 966.8 | 1,111.9 | 93.4 |
| Land Area | 0.6 | 1.6 | 3,531,905.4 |
| Water Area | 0.0 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Firth, ID | Lyman, WY | United States |
| Age 0 to 4 | 4.0% | 6.9% | 5.9% |
| Age 5 to 9 | 6.1% | 9.0% | 6.1% |
| Age 10 to 14 | 10.5% | 9.3% | 6.6% |
| Age 15 to 17 | 9.9% | 7.3% | 3.9% |
| Age 18 to 20 | 4.2% | 3.6% | 4.0% |
| Age 21 to 24 | 2.2% | 2.3% | 5.2% |
| Age 25 to 34 | 12.8% | 12.0% | 13.8% |
| Age 35 to 44 | 14.1% | 13.3% | 12.9% |
| Age 45 to 54 | 12.8% | 11.0% | 12.6% |
| Age 55 to 59 | 5.2% | 6.7% | 6.7% |
| Age 60 to 64 | 3.6% | 3.7% | 6.3% |
| Age 65 to 74 | 9.6% | 10.6% | 9.6% |
| Age 75 to 84 | 5.1% | 3.3% | 4.5% |
| Age 85 and over | 0.0% | 1.0% | 1.9% |
| space1 | | | |
| Race | | | |
| | Firth, ID | Lyman, WY | United States |
| White | 78.5% | 89.3% | 59.4% |
| Black | 0.0% | 0.0% | 12.2% |
| Asian | 0.4% | 0.0% | 5.6% |
| Native American | 2.7% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.0% | 0.4% |
| Two or More Races | 1.1% | 5.0% | 3.2% |
| Hispanic | 17.3% | 5.7% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Firth, ID | Lyman, WY | United States |
| Married Population | 55.9% | 63.7% | 49.8% |
| Currently Married | 55.0% | 63.4% | 48.0% |
| Married but Separated | 0.9% | 0.3% | 1.8% |
| Single Population | 44.1% | 36.3% | 50.2% |
| Never Married | 29.5% | 21.4% | 33.8% |
| Divorced | 11.4% | 10.6% | 10.8% |
| Widowed | 3.2% | 4.3% | 5.6% |
| space5 | | | |
| Household Size | 2.90 | 2.89 | 2.60 |
| Households | 191 | 598 | 124,010,992 |
| Family Households | 141 | 448 | 80,755,759 |
| Married couple, w/children | 52.5% | 55.1% | 30.5% |
| Married couple, no children | 29.8% | 34.6% | 42.9% |
| Non Family Households | 50 | 150 | 43,255,233 |
| Single householder, w/children | 7.8% | 6.0% | 15.8% |
| Single householder, no children | 9.9% | 4.2% | 10.8% |