| | Garrison, ND | Grantham, NH | United States |
| Population | 1,577 | 3,366 | 329,725,481 |
| Female Population | 49.0% | 53.1% | 50.5% |
| Male Population | 51.0% | 46.9% | 49.5% |
| Median Age | 50.5 | 50.1 | 38.4 |
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| Population - 2010 | 1,460 | 2,976 | 309,327,143 |
| Population - 2000 | 1,318 | 2,167 | 285,036,114 |
| Population - 1990 | 1,530 | 1,247 | 251,960,433 |
| Pop. 2000 to Now | 10.6% | 36.4% | 15.6% |
| Pop. 1990 to Now | -4.7% | 137.0% | 30.8% |
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| Population Density | 1,148.6 | 123.9 | 93.4 |
| Land Area | 1.4 | 27.2 | 3,531,905.4 |
| Water Area | 0.0 | 0.9 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Garrison, ND | Grantham, NH | United States |
| Age 0 to 4 | 6.5% | 0.0% | 5.9% |
| Age 5 to 9 | 9.3% | 8.5% | 6.1% |
| Age 10 to 14 | 2.2% | 9.4% | 6.6% |
| Age 15 to 17 | 2.3% | 5.3% | 3.9% |
| Age 18 to 20 | 1.8% | 4.5% | 4.0% |
| Age 21 to 24 | 3.8% | 2.4% | 5.2% |
| Age 25 to 34 | 13.3% | 1.4% | 13.8% |
| Age 35 to 44 | 5.5% | 13.3% | 12.9% |
| Age 45 to 54 | 8.8% | 14.5% | 12.6% |
| Age 55 to 59 | 8.5% | 13.8% | 6.7% |
| Age 60 to 64 | 8.3% | 6.1% | 6.3% |
| Age 65 to 74 | 10.7% | 11.5% | 9.6% |
| Age 75 to 84 | 11.7% | 7.8% | 4.5% |
| Age 85 and over | 7.2% | 1.5% | 1.9% |
| space1 | | | |
| Race | | | |
| | Garrison, ND | Grantham, NH | United States |
| White | 86.0% | 99.2% | 59.4% |
| Black | 2.5% | 0.0% | 12.2% |
| Asian | 0.1% | 0.0% | 5.6% |
| Native American | 8.7% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.0% | 0.4% |
| Two or More Races | 0.6% | 0.0% | 3.2% |
| Hispanic | 2.0% | 0.8% | 18.4% |
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| Marriage & Family | | | |
| | Garrison, ND | Grantham, NH | United States |
| Married Population | 54.2% | 70.7% | 49.8% |
| Currently Married | 53.9% | 67.0% | 48.0% |
| Married but Separated | 0.3% | 3.7% | 1.8% |
| Single Population | 45.8% | 29.3% | 50.2% |
| Never Married | 23.2% | 17.9% | 33.8% |
| Divorced | 14.3% | 4.0% | 10.8% |
| Widowed | 8.3% | 7.4% | 5.6% |
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| Household Size | 2.19 | 2.75 | 2.60 |
| Households | 689 | 1,224 | 124,010,992 |
| Family Households | 388 | 1,024 | 80,755,759 |
| Married couple, w/children | 22.7% | 34.4% | 30.5% |
| Married couple, no children | 54.6% | 58.0% | 42.9% |
| Non Family Households | 301 | 200 | 43,255,233 |
| Single householder, w/children | 21.1% | 4.1% | 15.8% |
| Single householder, no children | 1.5% | 3.5% | 10.8% |