| | Harlem, MT | La Monte, MO | United States |
| Population | 881 | 1,083 | 329,725,481 |
| Female Population | 49.6% | 56.5% | 50.5% |
| Male Population | 50.4% | 43.5% | 49.5% |
| Median Age | 39.3 | 25.6 | 38.4 |
| space3 | | | |
| Population - 2010 | 769 | 1,142 | 309,327,143 |
| Population - 2000 | 848 | 1,064 | 285,036,114 |
| Population - 1990 | 882 | 995 | 251,960,433 |
| Pop. 2000 to Now | -8.3% | 6.9% | 15.6% |
| Pop. 1990 to Now | -11.8% | 14.3% | 30.8% |
| space4 | | | |
| Population Density | 2,107.7 | 958.4 | 93.4 |
| Land Area | 0.4 | 1.1 | 3,531,905.4 |
| Water Area | 0.0 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Harlem, MT | La Monte, MO | United States |
| Age 0 to 4 | 7.3% | 14.2% | 5.9% |
| Age 5 to 9 | 4.3% | 6.3% | 6.1% |
| Age 10 to 14 | 9.5% | 4.0% | 6.6% |
| Age 15 to 17 | 1.5% | 5.3% | 3.9% |
| Age 18 to 20 | 8.4% | 7.5% | 4.0% |
| Age 21 to 24 | 5.1% | 12.1% | 5.2% |
| Age 25 to 34 | 9.5% | 10.6% | 13.8% |
| Age 35 to 44 | 13.1% | 13.6% | 12.9% |
| Age 45 to 54 | 11.0% | 10.0% | 12.6% |
| Age 55 to 59 | 8.9% | 3.9% | 6.7% |
| Age 60 to 64 | 4.7% | 3.3% | 6.3% |
| Age 65 to 74 | 12.0% | 5.6% | 9.6% |
| Age 75 to 84 | 4.0% | 3.1% | 4.5% |
| Age 85 and over | 0.8% | 0.6% | 1.9% |
| space1 | | | |
| Race | | | |
| | Harlem, MT | La Monte, MO | United States |
| White | 52.3% | 42.1% | 59.4% |
| Black | 0.0% | 0.0% | 12.2% |
| Asian | 0.5% | 0.3% | 5.6% |
| Native American | 36.8% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 1.5% | 0.2% |
| Other | 0.0% | 0.0% | 0.4% |
| Two or More Races | 4.1% | 1.8% | 3.2% |
| Hispanic | 6.4% | 54.3% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Harlem, MT | La Monte, MO | United States |
| Married Population | 47.1% | 46.6% | 49.8% |
| Currently Married | 42.7% | 44.9% | 48.0% |
| Married but Separated | 4.3% | 1.7% | 1.8% |
| Single Population | 53.0% | 53.4% | 50.2% |
| Never Married | 41.6% | 34.8% | 33.8% |
| Divorced | 4.3% | 13.3% | 10.8% |
| Widowed | 7.1% | 5.3% | 5.6% |
| space5 | | | |
| Household Size | 2.94 | 2.88 | 2.60 |
| Households | 297 | 376 | 124,010,992 |
| Family Households | 204 | 285 | 80,755,759 |
| Married couple, w/children | 22.5% | 38.2% | 30.5% |
| Married couple, no children | 40.2% | 22.8% | 42.9% |
| Non Family Households | 93 | 91 | 43,255,233 |
| Single householder, w/children | 23.0% | 21.1% | 15.8% |
| Single householder, no children | 14.2% | 17.9% | 10.8% |