SDCL § 15-2-6: Actions on state judgments and sealed instruments.

Except where, in special cases, a different limitation is prescribed by statute, the following civil actions other than for the recovery of real property can be commenced only within twenty years after the cause of action shall have accrued:

(1) An action upon a judgment or decree of any court of this state;

(2) An action upon a sealed instrument, except a real estate mortgage.