S.D. Codified Laws § 34-31A-46
The residents of any territory proposed to be annexed into a rural fire protection district may, by petition, call for an election on such annexation. The petition shall be signed by five percent of the voters residing within the territory included within the proposed annexation. The petition shall be submitted within twenty days of the district's governing body's vote to propose the annexation. The election shall be held within ninety days of the submission of the petition, but if the petition is submitted within one hundred twenty days of a regularly scheduled election of the rural fire protection district, the governing body of the rural fire protection district may place such question on the regular election ballot. The election on the annexation shall be voted upon only by those residing within the territory proposed to be annexed, and shall be decided by majority vote.
SDCL 34-31A-46