Many people who work with cannabis have heard the same story about the 1937 US ban. It says a newspaper owner, a chemical company and a banking family had the plant banned to protect their businesses. The story is easy to remember. It is often what first gets people interested in this history. Most of it, however, is not supported by documents from the time.
The documents point to less dramatic causes. These were prejudice against Mexican and Black Americans, a federal drug agency that wanted a bigger role, and a Congress that ignored the doctors who objected. Part 1 covers the 1937 law, the state laws that came before it and the doctors’ objection. Part 2 checks the conspiracy story one claim at a time.
This is United States legal history from 1937. It is not Thai law and does not apply in Thailand. In Thailand, cannabis flower (ช่อดอกกัญชา) is a controlled herb under the Notification of the Ministry of Public Health Re: Controlled Herbs (Cannabis), B.E. 2568. The Notification has been in force since 26 June 2025. Flower can be sold only with a prescription on form PT 33 (ภ.ท.33).
1. What the 1937 Law Said and How It Worked
The Marihuana Tax Act of 1937 is one of the better-documented US drug laws. Historians agree on its basic dates.
| Step | What happened |
|---|---|
| Bill introduced | H.R. 6385, on 14 April 1937, by Robert L. Doughton, a Democratic member of the House of Representatives from North Carolina |
| Hearings | Before the House Ways and Means Committee, which handles tax laws, on 27–30 April and 4 May 1937 |
| Revised bill | H.R. 6906, on 11 May 1937 |
| Who drafted it | The Treasury Department’s legal office (Office of General Counsel), under Herman Oliphant |
| Who pushed for it | Harry J. Anslinger, head of the Federal Bureau of Narcotics (FBN), the federal agency that would enforce the law |
| Signed | 2 August 1937, by President Franklin D. Roosevelt |
| In force | 1 October 1937 |
| Struck down | The US Supreme Court held key parts unconstitutional in Leary v. United States, 395 U.S. 6 (1969) |
| Repealed | By the Comprehensive Drug Abuse Prevention and Control Act of 1970 |
The taxes
Everyone in the cannabis trade had to register. Each group also paid an annual occupational tax, which was a yearly fee for the right to work with the plant.
| Who paid | Tax per year |
|---|---|
| Importers, manufacturers and compounders (people who mixed medicines) | $24 |
| Dealers | $3 |
| Producers (growers) | $1 |
| Physicians and other practitioners | $1 |
Each sale or handover also carried a transfer tax, which was a tax on every transfer of the plant:
- $1 per ounce (about 28 grams) if the buyer was registered;
- $100 per ounce if the buyer was not registered.
Breaking the law could mean a fine of up to $2,000 and up to five years in prison.
Why a tax law worked like a ban
On paper, the Act did not ban cannabis. It set up taxes and registration instead. In practice, the scheme was built so that complying was impractical or meant admitting to a crime.
Every grower, dealer and doctor had to file forms and pay the yearly tax. Anyone outside the registered system paid $100 per ounce. The Senate Finance Committee’s report on the bill openly said its purpose was to raise revenue and to discourage the widespread use of the drug by smokers and drug addicts.
This design is the reason the Act was struck down three decades later. The Fifth Amendment to the US Constitution protects people from being forced to give evidence against themselves. To comply with the Act, people had to declare in writing that they dealt in a plant that state laws already banned. In Leary (1969), the Supreme Court held that this broke the Fifth Amendment’s protection against self-incrimination.
Translator’s note: Thai cannabis rules also control the trade through licences, forms and records, not only through a plain “allowed” or “banned”. Before you apply for or renew a licence, list every form, record and fee the rule requires. That list shows you what compliance will really cost before you invest. Work from the rule itself, not from a summary. The topic Thai Cannabis Law and Compliance: Read the Original Legal Texts Before You Act or Post explains where to find the original Thai texts.
2. State and City Laws Came First, 1911–1937
The federal Act came after 25 years of state and city laws. It did not start the process. The best-documented steps are:
- Massachusetts, 1911: cannabis was added to a broader law. That law banned the sale of several drugs without a prescription.
- California, Maine, Wyoming and Indiana, 1913: In California, the change was a low-profile amendment to the state poison laws. The State Board of Pharmacy pushed it through. Historian Dale Gieringer links it to reform of pharmacy and narcotics law, not to Mexican immigration.
- El Paso (Texas), 1914: a city ordinance, often called the first local ban. Some accounts say it took effect in 1915.
- Texas, 1919: a law for the whole state, not just one city. It added “marihuana” to a general narcotics law.
Different reasons in different places
The reasons for these laws were not the same everywhere. In the US Southwest, one documented reason was migration from Mexico after the Mexican Revolution of 1910. Local newspapers, and some local laws, linked cannabis smoking to these newly arrived communities.
In other states, the early laws came out of general reform of drug and poison laws. Later, newspapers also linked cannabis to New Orleans and to Black jazz musicians.
These links were well established locally by the 1930s, when the FBN took up the issue. Historian David Musto wrote The American Disease (1973). Richard Bonnie and Charles Whitebread wrote The Marihuana Conviction (1974). Both books treat these racial links as central to the federal campaign.
Where the word “marihuana” came from
“Marihuana”, also spelled “mariguana”, is a Mexican Spanish word. Isaac Campos studied Mexico’s early drug laws in his book Home Grown (2012). He showed that the word appeared in English-language newspapers long before the 1930s.
Where the word first came from is still unsettled. One proposal traces it to Nahuatl, an Indigenous language of Mexico. Chris Duvall, in The African Roots of Marijuana (2019), argues for an African origin. He traces it to the Kimbundu word mariamba. The popular “María Juana” origin is generally regarded as a folk etymology. That means people made up the explanation because it sounds right, but there is no evidence for it.
The records show two things. By the 1930s, the word was used in ways that linked the plant with Mexican immigrants. The word was also written into federal law. There is no record showing that officials chose the word on purpose as a strategy.
Cannabis was already under international control
Cannabis was under international control before 1937. The 1925 International Opium Convention, signed in Geneva, covered “Indian hemp”. That was the treaty term for cannabis drug preparations. Egypt was the country that pushed hardest for this. The US position later fed into the 1961 Single Convention on Narcotic Drugs, the main UN drug treaty.
Translator’s note: The word “marihuana” helped hide which plant the bill was about. Thai rules can also cover different things depending on their definitions, such as flower, extract or hemp. Before you rely on a Thai rule, read its definitions section first. This tells you which plant parts and products the rule covers. It also stops you from applying a rule about extracts to flower, or the other way round.
3. The Doctors’ Objection, Which Popular Accounts Often Skip
Dr William Creighton Woodward was legislative counsel to the American Medical Association (AMA), the national association of US doctors. His job was to represent doctors before lawmakers. On 4 May 1937, he testified against the bill.
He made three main points:
- The evidence given to the committee did not back up the claims about addiction, violence and overdose.
- The law would make medical use of cannabis harder.
- The law would also hold back future research.
He also complained about how the bill was handled. The AMA had learned about it late and had not been consulted while it was drafted. The bill also used the word “marihuana”. Doctors did not readily link that word with the Cannabis medicines in their pharmacopoeia, the official reference book of medicines.
His warning about research came true. US cannabis research stayed heavily restricted for decades afterwards. Congress overrode his objections and passed the bill. Popular retellings often leave this out, even though it is well documented in the hearing record.
Translator’s note: One reason Woodward lost was that doctors learned about the bill too late to prepare. In Thailand, the draft Cannabis Control Act is not law yet. The Cabinet approved the draft on 22 September 2026 and sent it to the House of Representatives. Follow its progress through official announcements. Keep your own crop records and lab results organised. Then, if you comment on a draft rule, you can back your points with data you can show.
What Part 2 Covers
Part 2 checks each claim of the Hearst–DuPont–Mellon conspiracy story against the documents. It covers the February 1938 Popular Mechanics article and what historians see as the real causes. It also covers the US government’s own wartime hemp programme of 1942.
Sources for Part 1
- Taxation of Marihuana: Hearings before the Committee on Ways and Means, House of Representatives, 75th Congress, 1st Session, on H.R. 6385, 27–30 April and 4 May 1937 (includes the testimony of Dr William C. Woodward and H. J. Anslinger).
- US Senate, Committee on Finance, Report No. 900, 75th Congress (1937), on H.R. 6906: https://www.finance.senate.gov/imo/media/doc/75-900Rpt.pdf
- Leary v. United States, 395 U.S. 6 (1969).
- Richard J. Bonnie and Charles H. Whitebread II, The Marihuana Conviction: A History of Marihuana Prohibition in the United States (University Press of Virginia, 1974).
- David F. Musto, The American Disease: Origins of Narcotic Control (Yale University Press, 1973).
- Dale H. Gieringer, “The Forgotten Origins of Cannabis Prohibition in California”, Contemporary Drug Problems 26(2), 1999, pp. 237–288; revised version: The Origins of California's 1913 Cannabis Law - CaNorml.org
- Isaac Campos, Home Grown: Marijuana and the Origins of Mexico’s War on Drugs (University of North Carolina Press, 2012).
- Chris S. Duvall, The African Roots of Marijuana (Duke University Press, 2019).
This is an educational article on US regulatory history. It is general information, not legal advice.
Continued in Part 2: How the United States Banned Industrial Hemp in 1937: Checking the Hearst–DuPont–Mellon Conspiracy Theory Against the Documents (Part 2 of 2)