| | Plattsburg, MO | St. Joseph, MO | United States |
| Population | 2,296 | 73,138 | 329,725,481 |
| Female Population | 48.0% | 49.5% | 50.5% |
| Male Population | 52.0% | 50.6% | 49.5% |
| Median Age | 50.2 | 37.7 | 38.4 |
| space3 | | | |
| Population - 2010 | 2,316 | 76,657 | 309,327,143 |
| Population - 2000 | 2,354 | 73,990 | 285,036,114 |
| Population - 1990 | 2,248 | 71,852 | 251,960,433 |
| Pop. 2000 to Now | -4.8% | 0.1% | 15.6% |
| Pop. 1990 to Now | -0.3% | 3.1% | 30.8% |
| space4 | | | |
| Population Density | 637.6 | 1,661.1 | 93.4 |
| Land Area | 3.6 | 44.0 | 3,531,905.4 |
| Water Area | 0.0 | 0.8 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Plattsburg, MO | St. Joseph, MO | United States |
| Age 0 to 4 | 6.0% | 6.3% | 5.9% |
| Age 5 to 9 | 5.0% | 6.5% | 6.1% |
| Age 10 to 14 | 3.9% | 6.2% | 6.6% |
| Age 15 to 17 | 1.1% | 3.5% | 3.9% |
| Age 18 to 20 | 5.0% | 4.4% | 4.0% |
| Age 21 to 24 | 4.1% | 5.8% | 5.2% |
| Age 25 to 34 | 6.0% | 14.0% | 13.8% |
| Age 35 to 44 | 8.0% | 12.8% | 12.9% |
| Age 45 to 54 | 19.7% | 11.5% | 12.6% |
| Age 55 to 59 | 6.3% | 6.6% | 6.7% |
| Age 60 to 64 | 12.2% | 6.5% | 6.3% |
| Age 65 to 74 | 11.2% | 9.2% | 9.6% |
| Age 75 to 84 | 7.8% | 4.6% | 4.5% |
| Age 85 and over | 3.7% | 2.0% | 1.9% |
| space1 | | | |
| Race | | | |
| | Plattsburg, MO | St. Joseph, MO | United States |
| White | 83.4% | 80.2% | 59.4% |
| Black | 7.8% | 5.9% | 12.2% |
| Asian | 2.7% | 1.5% | 5.6% |
| Native American | 0.0% | 0.3% | 0.6% |
| Hawaiian, Pacific Islander | 0.2% | 0.5% | 0.2% |
| Other | 0.2% | 0.0% | 0.4% |
| Two or More Races | 4.4% | 4.0% | 3.2% |
| Hispanic | 1.2% | 7.5% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Plattsburg, MO | St. Joseph, MO | United States |
| Married Population | 47.9% | 43.6% | 49.8% |
| Currently Married | 44.7% | 42.0% | 48.0% |
| Married but Separated | 3.2% | 1.5% | 1.8% |
| Single Population | 52.1% | 56.4% | 50.2% |
| Never Married | 21.2% | 33.1% | 33.8% |
| Divorced | 18.9% | 17.3% | 10.8% |
| Widowed | 12.0% | 6.1% | 5.6% |
| space5 | | | |
| Household Size | 2.16 | 2.43 | 2.60 |
| Households | 1,039 | 28,594 | 124,010,992 |
| Family Households | 561 | 16,688 | 80,755,759 |
| Married couple, w/children | 25.5% | 27.5% | 30.5% |
| Married couple, no children | 43.5% | 41.5% | 42.9% |
| Non Family Households | 478 | 11,906 | 43,255,233 |
| Single householder, w/children | 8.4% | 22.3% | 15.8% |
| Single householder, no children | 22.6% | 8.7% | 10.8% |