| Place Name | San Mar |
| Place Type | Census Designated Place |
| ZIP Code(s) | 21713 |
| County | Washington County |
| Area Code(s) | 240,301 |
| Timezone | Eastern Daylight Time (EDT) |
| Population (2022) | 348 |
| Population Growth Rate (2010-19) | -4.69% |
| Majority Ethnicity | White 85.63% |
| Metro/Micro Stats Area | Hagerstown-Martinsburg, MD-WV |
| US Congressional District(s) | Maryland 6th |
| House of Delegates Districts | 2A |
| State Senate Districts | 2 |
| Race/Ethnicy | Percentage of Population (2021) |
|---|---|
| White | 85.63% |
| African American | 7.19% |
| Hispanic | 0% |
| Asian | 0% |
| Native American | 0% |
| Hawaiin/Pacific Islander | 7.19% |