S.D. Codified Laws § 7-2-1
A petition signed by fifteen percent of the registered voters of each of two or more adjoining counties of this state, based upon the total number of registered voters at the last preceding general election, requesting the formation of a committee to study the question of changing the boundary lines or of the consolidation of the petitioners' counties, pursuant to this chapter, must be filed with the county auditor of each affected county and presented to the board of county commissioners of their respective counties at the regular July meeting.
Each county auditor shall, within thirty days of receiving the petition, verify that the signatures on the petition are from registered voters of the county. A signature on a petition is invalid if signed more than six months before the date the petition is filed. If the auditor verifies that the petition meets the requirements of this section, the boards of county commissioners must appoint a study committee.
The petition must be filed with the county auditors of the counties prior to the first day of the regular July meeting of the board of county commissioners and must state the names of the counties to be consolidated or describe the boundary lines to be changed.
The auditor of each county where a petition is filed shall transmit a certified copy of the petition filed in that county to the auditor of each of any other affected county.
SDCL 7-2-1