| Place Name | Castalia |
| Place Type | Unincorporated Territory |
| ZIP Code(s) | 57369 |
| County | Charles Mix County |
| Area Code(s) | 605 |
| Timezone | Central Daylight Time (CDT) |
| Population (2021) | 75 |
| Majority Ethnicity | White 100% |
| US Congressional District(s) | South Dakota At-Large |
| State House Districts | 21 |
| State Senate Districts | 21 |
| Race/Ethnicy | Percentage of Population (2021) |
|---|---|
| White | 100% |
| African American | 0% |
| Hispanic | 0% |
| Asian | 0% |
| Native American | 0% |
| Hawaiin/Pacific Islander | 0% |