| Place Name | Mountain Plains |
| Place Type | Census Designated Place |
| ZIP Code(s) | 57783 |
| County | Lawrence County |
| Area Code(s) | 605 |
| Timezone | Mountain Daylight Time (MDT) |
| Population (2022) | 394 |
| Majority Ethnicity | White 99.66% |
| Metro/Micro Stats Area | Spearfish, SD |
| US Congressional District(s) | South Dakota At-Large |
| State House Districts | 31 |
| State Senate Districts | 31 |
| Race/Ethnicy | Percentage of Population (2021) |
|---|---|
| White | 99.66% |
| African American | 0% |
| Hispanic | 0% |
| Asian | 0% |
| Native American | 0% |
| Hawaiin/Pacific Islander | 0.34% |