Key Takeaways
- Cannabis was a legal, widely grown crop in America for over 200 years before prohibition
- Criminalization in the 1930s was driven more by politics, racism, and economics than by science or public health evidence, though genuine concerns about drug use, social disorder, and moral reform movements were also part of the era's context
- The 1970 Controlled Substances Act — which placed cannabis in Schedule I alongside heroin — was shaped significantly by political considerations, not solely by medical ones
- Decades of prohibition created enormous racial disparities in enforcement that persist today
- The current legalization wave represents the most significant reversal of drug policy in American history
The story of cannabis prohibition is not a story that begins with danger or addiction. It begins with hemp fields.
Cannabis sativa was cultivated across colonial America as a versatile industrial crop. Hemp fibre was used to make rope, sail canvas, and clothing. George Washington and Thomas Jefferson both grew it on their plantations. In 1619, the Virginia Assembly actually required farmers to grow hemp. Through the 18th and 19th centuries, cannabis-based tinctures and medicines were standard entries in the US Pharmacopeia — the official compendium of American medicines — used to treat pain, insomnia, and anxiety.
As late as 1900, there was no federal restriction on cannabis of any kind. It was sold openly in pharmacies and general stores across the country.
The shift from accepted crop to dangerous drug happened gradually, then suddenly — driven by a confluence of factors that included immigration anxiety, racial politics, economic interests, and genuine public concern about drug use and social order.
It is worth noting that the early 20th century was broadly an era of moral reform. Alcohol prohibition had passed in 1919, driven by temperance movements with real public support. Concerns about addiction, family breakdown, and social disorder were widespread and sincere — not simply manufactured. Cannabis prohibition emerged from this same cultural moment, making it difficult to separate cynical political manipulation from genuine moral concern. Both were present.
The Mexican connection. The word "marijuana" itself was largely unfamiliar to most Americans before the early 20th century. Cannabis was the term used by pharmacists and physicians. "Marijuana" (or "marihuana") was the Mexican Spanish term, and its deliberate adoption by prohibition advocates was not accidental — it was used to associate the plant with Mexican immigrants arriving in the Southwest following the Mexican Revolution. States bordering Mexico began passing anti-cannabis laws as early as 1913, framed in ways that reflected both immigration anxiety and broader concerns about social order.
Harry Anslinger and the Federal Bureau of Narcotics. The single most influential figure in cannabis prohibition was Harry Anslinger, appointed head of the newly formed Federal Bureau of Narcotics in 1930. Facing budget cuts and needing a cause to justify his agency's existence after alcohol prohibition ended, Anslinger launched a national campaign against cannabis. His rhetoric was often explicitly racial — he repeatedly linked cannabis use to Black jazz musicians and Mexican immigrants — but he also drew on broader public anxieties about youth drug use, crime, and moral decline that were genuinely present in American society at the time.
Reefer Madness. The 1936 film — originally titled Tell Your Children — exemplified the era's more sensationalist propaganda, portraying cannabis as a "killer weed" that drove users to violence and madness. The American Medical Association actually testified against the proposed federal ban in 1937, arguing the claims were exaggerated and that cannabis had legitimate medical uses. At the same time, not all opposition to cannabis in this period was cynical — some physicians and public health advocates had sincere concerns about unregulated drug use, even if the evidence base was thin.
The Marihuana Tax Act of 1937. Despite AMA opposition, Congress passed the Act with minimal debate, effectively criminalizing cannabis at the federal level by imposing prohibitive taxes and regulations. The era of legal cannabis in America was over.
For the next three decades, cannabis remained illegal but enforcement was relatively inconsistent. That changed dramatically in the late 1960s and early 1970s — a period of genuine social upheaval, rising drug use among youth, and widespread public concern about the direction of American society.
The Controlled Substances Act of 1970. The Nixon administration's Controlled Substances Act placed cannabis in Schedule I — the most restrictive category, reserved for drugs with "no currently accepted medical use" and "high potential for abuse" — alongside heroin, above cocaine and methamphetamine in terms of legal restriction.
The Schedule I classification was intended to be temporary, pending review by the Shafer Commission — a bipartisan panel Nixon himself appointed. The Commission's 1972 report, Marihuana: A Signal of Misunderstanding, recommended decriminalization for personal use, finding that cannabis did not meet the criteria for Schedule I. Nixon rejected the recommendation and never acted on it.
The political motivations behind the War on Drugs have been the subject of significant historical debate. A frequently cited piece of evidence is a 1994 interview with Nixon's domestic policy advisor John Ehrlichman, published in Harper's Magazine in 2016, in which he stated that the War on Drugs was designed partly to target Nixon's political enemies — Black people and antiwar activists — by associating them with drugs and criminalizing both heavily. The quote has become one of the most cited pieces of evidence regarding the political motivations behind the War on Drugs, though historians debate how much weight should be placed on a retrospective account given decades later by a convicted felon with his own complex legacy. What is less disputed is that enforcement patterns were racially skewed from the outset, and that the Schedule I classification was made without the scientific review that was promised.
The Reagan escalation. The 1980s brought mandatory minimum sentencing, asset forfeiture laws, and the "Just Say No" campaign. Federal cannabis penalties became dramatically harsher. The crack cocaine epidemic of the mid-1980s created genuine public fear about drug-related violence and addiction — concerns that were not simply manufactured, even as the policy responses to them were often disproportionate and racially uneven in application. Between 1980 and 1995, the US prison population quadrupled, with drug offenses driving much of the increase.
A peer-reviewed analysis in the Journal of Law and Health (Patton, 2021) documents how this period entrenched racial disparities in enforcement that persist decades later: Black Americans are still arrested for cannabis possession at significantly higher rates than white Americans, despite similar rates of use across racial groups.
The first crack in federal prohibition came from California. Proposition 215, passed by California voters in 1996, made California the first state to legalize medical cannabis — directly defying federal Schedule I classification. Patients with cancer, HIV/AIDS, and chronic pain gained legal access under state law, even as federal law remained unchanged.
The federal government fought back. The DEA raided dispensaries operating legally under state law. The Supreme Court ruled in Gonzales v. Raich (2005) that federal law superseded state medical cannabis laws.
Despite federal opposition, the medical cannabis movement spread. By 2012, 18 states had medical cannabis programs. The scientific literature on cannabis's medical potential — for pain, nausea, epilepsy, and other conditions — was growing. Public opinion was shifting, including among medical professionals who had previously been skeptical.
In November 2012, Colorado and Washington became the first states to legalize recreational cannabis for adults — a watershed moment in American drug policy. For the first time since 1937, adults in American states could legally purchase and possess cannabis for non-medical reasons.
The Obama administration responded with a policy of non-interference in states with robust regulatory frameworks. The Cole Memorandum (2013) instructed federal prosecutors to deprioritize enforcement in legal states, though it stopped short of changing federal law.
As of 2026, 24 states and Washington DC have legalized recreational cannabis, and 38 states have medical cannabis programs. Cannabis is now a multi-billion dollar legal industry — while simultaneously remaining a federal Schedule I controlled substance. This contradiction sits at the heart of current policy debates, and it creates real complications for banking, taxation, research, and interstate commerce that the industry continues to navigate.
Federal rescheduling. In 2024, the DEA proposed moving cannabis from Schedule I to Schedule III — a historic shift that would acknowledge its medical utility and reduce federal restrictions, though it would stop short of full federal legalization. The process remains ongoing as of 2026.
No history of US cannabis prohibition is complete without addressing its racial legacy — while also acknowledging that this remains an area of active policy debate rather than settled consensus.
The evidence that prohibition was built partly on racial targeting, and that enforcement was racially discriminatory over decades, is well-documented. Black Americans continue to be arrested for cannabis offenses at significantly higher rates than white Americans despite similar rates of use — a disparity that has persisted even as legalization has expanded.
At the same time, debates about how to address this legacy are genuinely contested. Questions about expungement of prior convictions, social equity licensing in the cannabis industry, and restorative investment in communities most affected by prohibition involve real tradeoffs — between speed and thoroughness, between individual remedy and systemic change, between state-level action and federal inaction. Reasonable people disagree about the right approaches, even among those who agree the disparities are real and serious.
Many legal states have introduced expungement programs to clear records of people convicted of offenses now legal under state law. Progress has been uneven — some states have automated expungement, others have made it a slow individual process. Criminal records for cannabis convictions continue to affect employment, housing, and voting rights for many Americans.
Understanding cannabis prohibition history is essential context for anyone following today's policy debates, medical research, or legal industry developments. It explains:
The arc of cannabis policy in America is one of the more striking examples of how policy shaped by a mix of genuine concern, propaganda, racial politics, and economic interest can take generations to reform — and how that reform, once underway, raises its own complex questions about justice, regulation, and public health.
When did cannabis become illegal in the US? Federally, with the Marihuana Tax Act of 1937, though several states criminalized it earlier — California in 1913 and Texas in 1919 — in contexts that reflected both immigration tensions and broader concerns about drug use.
Why is cannabis still Schedule I if so many states have legalized it? Federal law has not kept pace with state-level change. The Schedule I classification requires Congressional or DEA action to change. The DEA proposed moving cannabis to Schedule III in 2024, which would be the first federal rescheduling in over 50 years.
Were there racial motivations behind prohibition? Racial targeting was a documented component of both the initial criminalization in the 1930s and the enforcement of the War on Drugs. At the same time, historians generally acknowledge that genuine concerns about drug use and social order were also present — the two are not mutually exclusive.
Can people convicted of cannabis crimes get their records cleared? In many legal states, yes — through expungement programs. Federal convictions are harder to address. The process varies enormously by state, with some offering automatic expungement and others requiring individual petitions.
Is cannabis legal federally? No. As of 2026, cannabis remains a Schedule I controlled substance under federal law, regardless of state laws. Federal rescheduling to Schedule III is proposed but not yet finalized.
Cannabis prohibition in the United States emerged from a specific historical moment — one shaped by genuine social anxieties, racial politics, economic interests, and moral reform movements that were all present simultaneously. Separating these threads is not always straightforward, and historians continue to debate their relative weight. What is less disputed is that the policy consequences — particularly the racial disparities in enforcement and the suppression of medical research — have been profound and long-lasting.
The current legalization movement is, in many respects, a return toward the legal status cannabis held for most of American history. How that transition is managed — who benefits, who is remedied, and how the remaining federal-state contradiction is resolved — will define cannabis policy for the next generation.
This article is for informational purposes only.
Last updated: June 2026 | Primary sources and scholarship: Shafer Commission Report (1972); Patton D. et al., Journal of Law and Health (2021); US Congressional Records, Marihuana Tax Act Hearings (1937); Gonzales v. Raich, 545 U.S. 1 (2005); Cole Memorandum, US Department of Justice (2013)