| Place Name | Union Mill |
| Place Type | Census Designated Place |
| ZIP Code(s) | 20124 22030 22039 |
| County | Fairfax County |
| Area Code(s) | 571,703 |
| Timezone | Eastern Daylight Time (EDT) |
| Population (2022) | 4,362 |
| Majority Ethnicity | White 59.92% |
| Metro/Micro Stats Area | Washington-Arlington-Alexandria, DC-VA-MD-WV |
| US Congressional District(s) | Virginia 10thVirginia 11th |
| House of Delegates Districts | 40 |
| State Senate Districts | 37,39 |
| Race/Ethnicy | Percentage of Population (2021) |
|---|---|
| White | 59.92% |
| African American | 0.95% |
| Hispanic | 0% |
| Asian | 34.93% |
| Native American | 0% |
| Hawaiin/Pacific Islander | 4.19% |