S.D. Codified Laws § 12-4-9
The county auditor shall maintain and safeguard a file of voters in computer format that contains the information of each person registered in each voting precinct within the county. This file shall be known as the master registration file and shall be, at all times during office hours, open to public inspection. However, public access to social security numbers, driver license numbers, and dates of birth contained in the master registration file is prohibited. The master registration file shall contain all information from each voter's registration card. The master registration file shall also include the date of the last election the voter has voted in and when the voter's information was last updated. The master registration file may also contain additional voter history information. Any voter registration form for a purged or unregistered voter shall be kept for twenty-two months. No purged or unregistered voter may be included in the master registration file.
SDCL 12-4-9