Mountain Plains is an unincorporated area and census-designated place (CDP) in Lawrence County, South Dakota, United States.

[4] It was first listed as a CDP prior to the 2020 census.

It is bordered to the north by the city of Spearfish.

U.S. Route 14A forms the eastern edge of the CDP, following the canyon of Spearfish Creek.

This South Dakota state location article is a stub.