S.D. Codified Laws § 47-1A-1105

A domestic parent corporation that owns shares of a domestic or foreign subsidiary corporation that carry at least ninety percent of the voting power of each class and series of the outstanding shares of the subsidiary that have voting power may merge the subsidiary into itself or into another such subsidiary, or merge itself into the subsidiary, without the approval of the board of directors or shareholders of the subsidiary, unless the articles of incorporation of any of the corporations otherwise provide, and unless, in the case of a foreign subsidiary, approval by the subsidiary's board of directors or shareholders is required by the laws under which the subsidiary is organized.