| | Montpelier, ID | Grangeville, ID | United States |
| Population | 2,610 | 3,296 | 329,725,481 |
| Female Population | 50.7% | 49.6% | 50.5% |
| Male Population | 49.3% | 50.4% | 49.5% |
| Median Age | 35.5 | 41.7 | 38.4 |
| space3 | | | |
| Population - 2010 | 2,588 | 3,158 | 309,327,143 |
| Population - 2000 | 2,785 | 3,228 | 285,036,114 |
| Population - 1990 | 2,656 | 3,226 | 251,960,433 |
| Pop. 2000 to Now | -9.2% | 1.0% | 15.6% |
| Pop. 1990 to Now | -4.8% | 1.1% | 30.8% |
| space4 | | | |
| Population Density | 1,126.0 | 2,201.7 | 93.4 |
| Land Area | 2.3 | 1.5 | 3,531,905.4 |
| Water Area | 0.0 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Montpelier, ID | Grangeville, ID | United States |
| Age 0 to 4 | 7.1% | 9.4% | 5.9% |
| Age 5 to 9 | 7.4% | 6.2% | 6.1% |
| Age 10 to 14 | 6.2% | 6.2% | 6.6% |
| Age 15 to 17 | 6.4% | 3.6% | 3.9% |
| Age 18 to 20 | 5.5% | 5.2% | 4.0% |
| Age 21 to 24 | 6.0% | 6.9% | 5.2% |
| Age 25 to 34 | 10.3% | 5.6% | 13.8% |
| Age 35 to 44 | 12.1% | 9.9% | 12.9% |
| Age 45 to 54 | 12.5% | 10.6% | 12.6% |
| Age 55 to 59 | 5.9% | 6.4% | 6.7% |
| Age 60 to 64 | 4.5% | 8.8% | 6.3% |
| Age 65 to 74 | 8.6% | 10.0% | 9.6% |
| Age 75 to 84 | 6.4% | 9.9% | 4.5% |
| Age 85 and over | 1.1% | 1.3% | 1.9% |
| space1 | | | |
| Race | | | |
| | Montpelier, ID | Grangeville, ID | United States |
| White | 92.1% | 85.6% | 59.4% |
| Black | 0.0% | 0.1% | 12.2% |
| Asian | 0.3% | 0.0% | 5.6% |
| Native American | 0.0% | 4.3% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.0% | 0.4% |
| Two or More Races | 0.7% | 1.5% | 3.2% |
| Hispanic | 6.9% | 8.4% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Montpelier, ID | Grangeville, ID | United States |
| Married Population | 55.6% | 56.7% | 49.8% |
| Currently Married | 54.3% | 56.7% | 48.0% |
| Married but Separated | 1.3% | 0.0% | 1.8% |
| Single Population | 44.4% | 43.3% | 50.2% |
| Never Married | 25.3% | 18.5% | 33.8% |
| Divorced | 12.8% | 14.5% | 10.8% |
| Widowed | 6.3% | 10.3% | 5.6% |
| space5 | | | |
| Household Size | 2.71 | 2.38 | 2.60 |
| Households | 952 | 1,358 | 124,010,992 |
| Family Households | 651 | 914 | 80,755,759 |
| Married couple, w/children | 30.7% | 33.7% | 30.5% |
| Married couple, no children | 51.5% | 42.6% | 42.9% |
| Non Family Households | 301 | 444 | 43,255,233 |
| Single householder, w/children | 13.5% | 12.8% | 15.8% |
| Single householder, no children | 4.3% | 10.9% | 10.8% |