| | Union, NJ | Florham Park, NJ | United States |
| Population | 6,514 | 12,655 | 329,725,481 |
| Female Population | 51.1% | 51.7% | 50.5% |
| Male Population | 48.9% | 48.3% | 49.5% |
| Median Age | 45.3 | 40.6 | 38.4 |
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| Population - 2010 | 5,891 | 11,824 | 309,327,143 |
| Population - 2000 | 6,160 | 8,857 | 285,036,114 |
| Population - 1990 | 5,078 | 8,521 | 251,960,433 |
| Pop. 2000 to Now | -8.3% | 33.5% | 15.6% |
| Pop. 1990 to Now | 11.2% | 38.8% | 30.8% |
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| Population Density | 347.7 | 1,731.7 | 93.4 |
| Land Area | 18.7 | 7.3 | 3,531,905.4 |
| Water Area | 1.9 | 0.2 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Union, NJ | Florham Park, NJ | United States |
| Age 0 to 4 | 2.6% | 4.4% | 5.9% |
| Age 5 to 9 | 2.8% | 4.7% | 6.1% |
| Age 10 to 14 | 4.4% | 4.3% | 6.6% |
| Age 15 to 17 | 7.2% | 3.9% | 3.9% |
| Age 18 to 20 | 6.4% | 10.0% | 4.0% |
| Age 21 to 24 | 6.9% | 9.1% | 5.2% |
| Age 25 to 34 | 10.2% | 9.2% | 13.8% |
| Age 35 to 44 | 9.1% | 10.6% | 12.9% |
| Age 45 to 54 | 16.2% | 11.6% | 12.6% |
| Age 55 to 59 | 10.2% | 7.4% | 6.7% |
| Age 60 to 64 | 5.5% | 6.0% | 6.3% |
| Age 65 to 74 | 9.9% | 9.1% | 9.6% |
| Age 75 to 84 | 7.6% | 5.7% | 4.5% |
| Age 85 and over | 1.1% | 4.1% | 1.9% |
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| Race | | | |
| | Union, NJ | Florham Park, NJ | United States |
| White | 83.1% | 72.1% | 59.4% |
| Black | 9.1% | 5.2% | 12.2% |
| Asian | 2.5% | 11.7% | 5.6% |
| Native American | 0.2% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.8% | 0.3% | 0.4% |
| Two or More Races | 1.8% | 1.8% | 3.2% |
| Hispanic | 2.5% | 9.0% | 18.4% |
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| Marriage & Family | | | |
| | Union, NJ | Florham Park, NJ | United States |
| Married Population | 47.6% | 48.6% | 49.8% |
| Currently Married | 47.2% | 48.1% | 48.0% |
| Married but Separated | 0.4% | 0.5% | 1.8% |
| Single Population | 52.4% | 51.4% | 50.2% |
| Never Married | 40.9% | 37.6% | 33.8% |
| Divorced | 7.2% | 7.6% | 10.8% |
| Widowed | 4.3% | 6.2% | 5.6% |
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| Household Size | 2.42 | 2.49 | 2.60 |
| Households | 2,108 | 4,391 | 124,010,992 |
| Family Households | 1,530 | 2,893 | 80,755,759 |
| Married couple, w/children | 26.9% | 37.1% | 30.5% |
| Married couple, no children | 60.1% | 47.6% | 42.9% |
| Non Family Households | 578 | 1,498 | 43,255,233 |
| Single householder, w/children | 5.2% | 8.0% | 15.8% |
| Single householder, no children | 7.8% | 7.3% | 10.8% |