| | Kirby, VT | Bigfork, MT | United States |
| Population | 808 | 4,683 | 329,725,481 |
| Female Population | 45.3% | 52.8% | 50.5% |
| Male Population | 54.7% | 47.2% | 49.5% |
| Median Age | 38.4 | 54.7 | 38.4 |
| space3 | | | |
| Population - 2010 | 489 | 4,401 | 309,327,143 |
| Population - 2000 | 456 | 1,421 | 285,036,114 |
| Population - 1990 | 347 | 2,723 | 251,960,433 |
| Pop. 2000 to Now | 7.2% | 272.5% | 15.6% |
| Pop. 1990 to Now | 40.9% | 94.4% | 30.8% |
| space4 | | | |
| Population Density | 33.2 | 149.8 | 93.4 |
| Land Area | 24.4 | 31.3 | 3,531,905.4 |
| Water Area | 0.0 | 6.1 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Kirby, VT | Bigfork, MT | United States |
| Age 0 to 4 | 6.6% | 1.7% | 5.9% |
| Age 5 to 9 | 12.3% | 3.5% | 6.1% |
| Age 10 to 14 | 3.5% | 4.2% | 6.6% |
| Age 15 to 17 | 3.2% | 5.0% | 3.9% |
| Age 18 to 20 | 3.8% | 2.8% | 4.0% |
| Age 21 to 24 | 4.5% | 5.7% | 5.2% |
| Age 25 to 34 | 10.1% | 9.2% | 13.8% |
| Age 35 to 44 | 13.4% | 7.0% | 12.9% |
| Age 45 to 54 | 9.9% | 11.3% | 12.6% |
| Age 55 to 59 | 5.6% | 10.5% | 6.7% |
| Age 60 to 64 | 11.4% | 8.8% | 6.3% |
| Age 65 to 74 | 13.4% | 17.4% | 9.6% |
| Age 75 to 84 | 2.0% | 8.8% | 4.5% |
| Age 85 and over | 0.5% | 4.1% | 1.9% |
| space1 | | | |
| Race | | | |
| | Kirby, VT | Bigfork, MT | United States |
| White | 97.6% | 86.0% | 59.4% |
| Black | 0.0% | 0.1% | 12.2% |
| Asian | 0.0% | 0.1% | 5.6% |
| Native American | 0.0% | 0.2% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 1.1% | 0.4% |
| Two or More Races | 1.0% | 1.8% | 3.2% |
| Hispanic | 1.4% | 10.6% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Kirby, VT | Bigfork, MT | United States |
| Married Population | 66.9% | 54.1% | 49.8% |
| Currently Married | 66.4% | 53.7% | 48.0% |
| Married but Separated | 0.5% | 0.4% | 1.8% |
| Single Population | 33.1% | 45.9% | 50.2% |
| Never Married | 23.2% | 24.1% | 33.8% |
| Divorced | 7.6% | 11.4% | 10.8% |
| Widowed | 2.2% | 10.4% | 5.6% |
| space5 | | | |
| Household Size | 2.86 | 2.15 | 2.60 |
| Households | 283 | 2,152 | 124,010,992 |
| Family Households | 226 | 1,220 | 80,755,759 |
| Married couple, w/children | 28.3% | 23.9% | 30.5% |
| Married couple, no children | 57.5% | 63.3% | 42.9% |
| Non Family Households | 57 | 932 | 43,255,233 |
| Single householder, w/children | 11.5% | 4.3% | 15.8% |
| Single householder, no children | 2.7% | 8.4% | 10.8% |