South Dakota Codified Laws
Chapter 09 - Actions For Specific Performance
Section 21-9-8 - Performance or offer to perform in lieu of signature of written contract.

21-9-8. Performance or offer to perform in lieu of signature of written contract.
A party who has signed a written contract may be compelled specifically to perform it, though the other party has not signed it, if the latter has performed, or offers to perform it on his part, and the case is otherwise proper for enforcing specific performance.

Source: CivC 1877, §1997; CL 1887, §4630; RCivC 1903, §2342; RC 1919, §2013; SDC 1939 & Supp 1960, §37.4606.