S.D. Codified Laws § 50-7-7
If the question of establishing a county airport has not previously been approved by a majority vote of the voters at an election at which the question was submitted, then any county desiring to establish and construct an airport shall state in the next published report of the county's proceedings the county's intention to establish and construct the airport stating the maximum amount which might be required to do so. If within sixty days from the publication a protest signed by fifteen percent of the voters of the county voting at the last general election for Governor be filed with the county commissioners, then no action may be taken until the question has been submitted to a vote of the people and sixty percent of those voting shall vote in favor thereof. The question to be so submitted shall be, "Shall the county expend an amount not to exceed $________ to establish and construct an airport?"
SDCL 50-7-7