Cannabis in South Dakota is illegal for all purposes, and possession of any amount is a criminal offense. South Dakota is the only U.S. state which outlaws ingestion of controlled substances. Testing positive for cannabis can be a misdemeanor offense.
As part of a larger trend nationwide to restrict cannabis, South Dakota banned the drug in 1933.
Decriminalization and repeal (1977)
In 1977, during a short-lived wave of decriminalization in the country, South Dakota decriminalized cannabis, but repealed that law "almost immediately" afterward.
Medical cannabis attempts (2006–2015)
Ballot initiatives to legalize medical marijuana appeared on the 2006 and 2010 election ballots in South Dakota, but failed both times. The 2006 initiative lost 52%-47%, while the 2010 initiative lost 63%-36%. Cannabis activist Emmett Reistroffer commented that the decrease of support in 2010 was due in part to the rise of the Tea Party movement and the presence of an anti-cigarette smoking bill on the same ballot.
In mid-2015, there was an effort to place yet another ballot initiative on the 2016 election to legalize medical marijuana, but unlike in 2006 and 2010, the Marijuana Policy Project did not anticipate financially supporting the initiative due to strong cannabis campaigns in other states requiring attention for that election.
In mid-2015, South Dakotans Against Prohibition began circulating petitions to put decriminalization of marijuana on the November 2016 ballot, reclassifying possession of one ounce or less a civil, rather than criminal, infraction, and remove penalties for paraphernalia and consumption. However, SDAP failed to gather the 13,871 signatures necessary to place an initiated measure on the ballot and stated it would withdraw its petition.
2018 medical cannabis ballot initiative
In November 2017, activists turned in over 15,000 signatures, narrowly meeting valid signature requirements, in order to place medical cannabis on the 2018 ballot. The initiative failed to make the ballot due to an insufficient number of valid signatures. 
2020 medical cannabis ballot initiative
Recreational legalization on the Flandreau Santee Sioux Tribe reservation
In mid-2015, the Flandreau Santee Sioux Tribe, located in eastern South Dakota, stated their intent to begin growing cannabis on one authorized site on their reservation, and commence selling the product on 1 January 2016, following a vote of tribal authorities which decided 5–1 to legalize cannabis. Facing legal uncertainties, the tribe destroyed millions of dollars worth of marijuana on November 7, 2015.
- Gross, Scott (5 February 2017). "Only in South Dakota, possession by ingestion". KOTA-TV. Retrieved 9 December 2017.
- Walker, Mark (5 May 2016). "Report: S.D. drug laws hurt prison reform efforts". Argus Leader. Retrieved 9 December 2017.
- Richard Davenport-Hines (10 November 2003). The Pursuit of Oblivion: A Global History of Narcotics. W.W. Norton. pp. 240–. ISBN 978-0-393-32545-4.
- David R. Bewley-Taylor (22 March 2012). International Drug Control: Consensus Fractured. Cambridge University Press. pp. 169–. ISBN 978-1-107-37907-7.
- "South Dakota Medical Marijuana, Initiative 4 (2006)". ballotpedia.org.
- "South Dakota Medical Marijuana, Initiative 13 (2010)". ballotpedia.org.
- "Medical marijuana gains a strategy in S.D." Argus Leader. 23 November 2014.
- Seth Tupper Journal staff. "Medical marijuana: a look at ballot's chances of passage in South Dakota". Rapid City Journal.
- Kevin Burbach, Associated Press (30 July 2015). "Campaign to ease South Dakota marijuana laws kicks off". Argus Leader.
- Kevin Larsen, KCCR Radio (1 Nov 2015). "Campaign To Ease South Dakota Marijuana Law Fails To Reach Required Signatures". KCCR Radio. Archived from the original on 4 March 2016. Retrieved 8 November 2015.
- Anndrea Anderson (5 Nov 2015). "Ballot Petitions: Some Turned In, Some Still Circulating, One Withdrawn". KDLT TV.
- "1 of 3 marijuana initiatives passes first hurdle for South Dakota 2018 ballot". The Cannabist. November 7, 2017.
- "South Dakota Medical Marijuana Initiative (2018)". Ballotpedia.
- South Dakota Initiated Measure 26, Medical Marijuana Initiative (2020), Ballotpedia. Accessed December 20, 2019
- Garcia, Regina (2015-06-17). "South Dakota Indian tribe plans to sell marijuana by Jan. 1". Thecannabist.co. Retrieved 2015-07-12.
- "Developing: Santee Sioux Tribe Burning Millions In Marijuana". KELO-TV. 2015-11-07. Retrieved 2015-11-07.