Surprise Valley township
- County:
- Mellette County
- County Seat:
- No
- Area (mi²):
- 33.505
- State:
- South Dakota
Surprise Valley township is located in Mellette County, South Dakota. Surprise Valley township has a 2026 population of 15. Surprise Valley township is currently declining at a rate of 0% annually and its population has increased by 7.14% since the most recent census, which recorded a population of 14 in 2020.
The median age in Surprise Valley township is 72.3 years: 0 years for males, and 0 years for females. For every 100 females there are 127.3 males.