S.D. Codified Laws § 49-30-16
In the case of rural telephone companies where it is no longer possible, by reasonable diligence, to procure the attendance in person or by proxy of the owners of the proper majority of the shares of all the subscribed capital stock as shown by the books of the company, or a proper majority of the members if there be no capital stock, by reason of death, removal from the state, or the whereabouts of a stockholder or member being unknown, a lesser number of stockholders or members may meet, elect a board of directors and transact any other business necessary to the proper conduct of the telephone company or association or vote on resolutions to reorganize or dissolve the corporation, sell the corporate assets and repeal or amend the articles of incorporation, with the same force and effect as though a proper majority of such stockholders and members were present; provided further, any action taken by a lesser number than a proper majority shall not be binding upon the company or association unless at least two-thirds of all stockholders or members whose respective post-office address is known are represented in person or by proxy. An affidavit by the secretary or treasurer of the company or association generally stating that all of the members or stockholders of the company or association cannot be found and further stating the number of members or stockholders whose whereabouts are known, will be proof of reasonable diligence for the purposes of this section and certify the authority of the lesser number of known stockholders or members to so vote.
SDCL 49-30-16