S.D. Codified Laws § 47-1A-1202

A sale, lease, exchange, or other disposition of assets, other than a disposition described in § 47-1A-1201, requires approval of the corporation's shareholders if the disposition would leave the corporation without a significant continuing business activity. If a corporation retains a business activity that represented at least twenty-five percent of total assets at the end of the most recently completed fiscal year, and twenty-five percent of either income from continuing operations before taxes or revenues from continuing operations for that fiscal year, in each case of the corporation and its subsidiaries on a consolidated basis, the corporation will conclusively be deemed to have retained a significant continuing business activity.