S.D. Codified Laws § 11-4-5
If a zoning ordinance is adopted, the ordinance is subject to the provisions of § 9-19-7 as a comprehensive regulation unless the referendum is invoked, or unless a written protest is filed with the auditor or clerk, signed by at least forty percent of the owners of equity in the lots included in any proposed district and the lands within two hundred fifty feet from any part of the proposed district. A corporation is construed to be a sole owner, and if parcels of land are in the name of more than one person, ownership representation is in proportion to the number of signers who join in the petition in relation to the number of owners. If a protest is filed, the ordinance does not become effective unless the ordinance is approved by two-thirds of the governing body of the municipality. The protest provisions of this section do not apply to any ordinance regulating or establishing flood plain areas.
SDCL 11-4-5