Cannabis in South Dakota will be legal for both medical and recreational use on July 1, 2021, having been legalized by a pair of ballot initiatives on November 3, 2020. Prior to then, cannabis was illegal for all purposes, with South Dakota being the only U.S. state which outlawed ingestion of controlled substances. Testing positive for cannabis could be a misdemeanor offense. South Dakota became the first state in US history to legalize recreational and medical cannabis simultaneously.
As part of a larger trend nationwide to restrict cannabis, South Dakota banned the drug in 1931.
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In 1977, during a short-lived wave of decriminalization in the country, South Dakota decriminalized cannabis, but repealed that law "almost immediately" afterward.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 (SDAP) began circulating petitions to put decriminalization of marijuana on the November 2016 ballot, reclassifying possession of one ounce (28 g) 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 cannabis ballot initiative
Both measures, coming in effect on July 1, 2021, were passed by voters with a 69.9% margin in favor for Initiated Measure 26 and 54.2% for Constitutional Amendment A, respectively. South Dakota therefore became the first state to go from a prohibition state to a legalization state, leapfrogging their way around many obstacles that other states go through to legalize cannabis.
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.
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South Dakota became the first state in the country to legalize medical and adult-use marijuana simultaneously during Tuesday’s election.
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South Dakota voters will decide whether or not to legalize marijuana in the state.
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South Dakota made history Tuesday when it became the first state to legalize both medical and adult-use marijuana on the same day.
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