S.D. Codified Laws § 31-12A-16
There shall be elected from among the eligible voters of the district at the first election of a road district, held pursuant to § 6-16-5 or 6-16-5.2, three trustees at large, who shall respectively hold their offices, one for a term of one year, one for a term of two years, and one for a term of three years. The person having the highest number of votes shall serve for a term of three years, the person receiving the second highest number of votes shall serve for a term of two years, and the person receiving the third highest number of votes shall serve for a term of one year, and such persons shall be declared elected to such offices. Thereafter, in accordance with §§ 31-12A-15 and 31-12A-15.1, there shall be elected annually one trustee for a term of three years. The judges shall subscribe and certify a statement of the persons elected to fill the offices of trustees in the road district and file the statement with the county auditor within ten days after the date of the election.
SDCL 31-12A-16