Why Is Cannabis Illegal? A History of Marijuana Prohibition in America

Cannabis became illegal in America through a sequence of federal policies driven more by politics and racism than scientific evidence. The Marihuana Tax Act of 1937 first restricted the plant through taxation, and the Controlled Substances Act of 1970 placed it in Schedule I — the most restrictive category — where it remains today. Understanding this history reveals why a plant used medicinally for over a century became a federal crime.

Cannabis in Early America: A Respectable Medicine

Before the 20th century, cannabis was a routine product in American pharmacies and homes. It appeared in the United States Pharmacopeia from 1850 onward, sold as a tincture for ailments ranging from migraines to insomnia. Farmers grew it for rope, textiles, and paper — the word "canvas" itself derives from cannabis. There was nothing controversial about it.

This respectability began to shift as Mexican immigrants arrived during the early 20th century, bringing the practice of smoking cannabis with them. During the Great Depression, economic anxiety fueled anti-immigrant sentiment, and cannabis became associated with the communities arriving from the south. The plant's name even changed — "marijuana" (a Spanish-derived term) replaced "cannabis" in public discourse, distancing it from its medical and industrial roots. History.com

Early federal attention to cannabis came through taxation rather than bans. The Harrison Act of 1914 targeted opiates and cocaine, but did not yet include cannabis. It was the combination of xenophobia, economic interests, and a changing media landscape that set the stage for the first federal assault on the plant.

Key facts about early cannabis use in America:

• Listed in the United States Pharmacopeia from 1850 onward
• Sold as tinctures in pharmacies for common ailments
• Used by farmers for rope, textiles, and paper production
• The word "canvas" derives from the Latin word for cannabis

Harry Anslinger and the Birth of Federal Cannabis Prohibition

When alcohol prohibition ended in 1933, the Bureau of Prohibition faced an identity crisis. Harry Anslinger, who had worked in customs enforcement, took over the remnants of that agency and renamed it the Federal Bureau of Narcotics. He needed a new target to justify his agency's existence — and he found it in cannabis.

Anslinger became the country's most vocal opponent of marijuana, and his methods shaped the debate for decades. He testified before Congress, wrote inflammatory articles, and seeded newspapers with stories linking cannabis to violent crime. His rhetoric was explicit: he described users as dangerous, and his campaigns disproportionately targeted Black Americans and Mexican immigrants. PBS Frontline

Anslinger built relationships with publishers and newspapers, ensuring his message reached every corner of the country. He was remarkably candid in private, once stating that the goal was to eliminate cannabis — not regulate it. His agency needed a problem to solve, and cannabis became that problem.

This era also gave rise to the "reefer madness" phenomenon — sensationalized news stories and films depicting cannabis as a drug that caused madness, violence, and moral degradation. While these accounts were wildly exaggerated and often racist, they were effective at generating public fear. The cultural groundwork was being laid for federal action.

Harry Anslinger's tactics included:

• Testifying before Congress with inflammatory claims
• Writing articles linking cannabis to violent crime
• Seeding newspapers with sensationalist stories
• Disproportionately targeting Black and Mexican communities

The 1937 Marihuana Tax Act: How It Worked

The first federal action against cannabis came not as an outright ban, but as a clever tax measure. The Marihuana Tax Act of 1937 imposed steep financial burdens on anyone handling the plant — from growers to doctors to pharmacists. Rather than explicitly criminalizing possession, the law made compliance so expensive and bureaucratically complex that legal cannabis essentially became impossible. Wikipedia

The Act required dealers to register with the federal government, pay excise taxes, and maintain detailed records. Violations carried heavy penalties, including prison time. It was a workaround — Congress found it easier to regulate cannabis through taxation than through explicit criminalization, avoiding constitutional questions about interstate commerce authority.

The law was also retroactive in practice. Anyone who had possessed cannabis before the law took effect could be prosecuted for failing to pay the tax — a strategy that criminalized behavior that was legal just months before. This legislative sleight of hand allowed prohibition to arrive without ever calling it prohibition.

Farmers, particularly in the South and Midwest, lost access to hemp that had been a standard crop for generations. The timber and cotton industries, which had long competed with hemp paper and textiles, welcomed the restrictions. The Act passed with little public debate and minimal scientific input — fear, not evidence, drove the vote.

How the Marihuana Tax Act worked:

• Required federal registration for all cannabis handlers
• Imposed steep excise taxes on transactions
• Made compliance so costly it effectively banned the plant
• Criminalized retroactive possession through tax violations

1970 and the Controlled Substances Act: Cannabis Gets Scheduled

Forty years after the Marihuana Tax Act, cannabis found itself at the center of a major federal overhaul of drug policy. Richard Nixon's War on Drugs, declared in 1971, escalated enforcement dramatically, and the Controlled Substances Act of 1970 created the framework still in use today. NIAAA Alcohol Policy Information System

The CSA established five schedules based on a substance's abuse potential and medical utility. Cannabis was placed in Schedule I — the most restrictive category — defined as having a high potential for abuse, no currently accepted medical use, and a lack of accepted safety for use under medical supervision. U.S. Drug Enforcement Administration

This classification was not the result of new scientific findings. It reflected political convenience: putting cannabis in the highest schedule satisfied hardliners in Nixon's coalition while avoiding the appearance of being soft on drugs. The scheduling was largely symbolic — it was a statement that cannabis had no legitimate use, not a conclusion reached through medical review.

The practical effect was severe. Research on cannabis became nearly impossible, as scientists needed special DEA approval and NIDA oversight to study it. The Schedule I designation created a Catch-22: you could not prove medical value because you could not legally research it, and because you could not prove medical value, it remained Schedule I.

Comparison of federal drug scheduling:

Schedule	Definition	Cannabis Status
Schedule I	High abuse potential, no medical use, unsafe	Cannabis is classified here
Schedule II	High abuse potential, some accepted medical uses	narcotics like oxycodone
Schedule III	Moderate abuse potential, accepted medical uses	steroids, ketamine
Schedule IV	Low abuse potential, accepted medical uses	Xanax, Valium
Schedule V	Lowest abuse potential, accepted medical uses	cough preparations

The War on Drugs: Mass Incarceration and Disparate Impact

The decades following the CSA brought aggressive enforcement at the federal and state levels. The 1986 Anti-Drug Abuse Act imposed mandatory minimum sentences for drug offenses that had no relation to the severity or harm of the offense. Simple possession of small amounts of cannabis could carry years in federal prison.

The racial disparities were immediate and stark. Despite comparable usage rates between Black and white Americans, Black Americans were arrested, prosecuted, and incarcerated at significantly higher rates. The 4-to-1 arrest disparity reflected a system that targeted communities of color for enforcement in ways that white users largely escaped. History.com

The consequences extended far beyond prison sentences. Convictions destroyed employment prospects, housing eligibility, and voting rights. The "war on drugs" created a permanent underclass, with criminal records preventing full participation in civic life. States spent billions annually enforcing cannabis laws — money that could have supported education, healthcare, or infrastructure.

This era defined a generation's relationship with cannabis. What had been a social activity in many communities became a criminal offense that followed people for life. The damage done to families and communities is still being measured — and the legalization movement is, in part, a response to the failures of that enforcement-first approach.

The human cost of cannabis criminalization:

• Millions of arrests for possession alone
• 4-to-1 racial disparity in arrest rates despite equal usage
• Criminal records that bar employment, housing, and voting rights
• Billions spent annually on enforcement instead of public health

The Tide Turns: State-Level Legalization and What Comes Next

California's 1996 medical cannabis initiative marked the beginning of the end for prohibition at the state level. It was the first crack in the wall, and it did not take long for others to follow. Today, more than 25 states and Washington D.C. have legalized recreational cannabis, with most states allowing some form of medical use. NIAAA Alcohol Policy Information System

The momentum has been remarkable in speed and scale. What was once a fringe issue has become mainstream — polling consistently shows majority support for legalization across party lines. States that legalized have generally seen stronger tax revenues, reduced arrest disparities, and a regulated market that replaced the underground economy.

Yet federal prohibition remains. Cannabis is still a Schedule I substance under the CSA, making it illegal at the federal level regardless of state law. This creates a patchwork system with significant practical problems. Cannabis businesses cannot access standard banking services, rely on cash-only operations, and face unique tax burdens under Section 280E of the tax code that deny standard business deductions.

The result is an awkward middle ground: legal in most of the country but a federal crime everywhere, subject to conflicting state and federal enforcement priorities. Reform efforts at the federal level — including SAFE Banking Act and descheduling proposals — have repeatedly stalled, leaving the current patchwork in place.

Current state of cannabis legalization:

• 25+ states and Washington D.C. have legalized recreational cannabis
• Most states permit medical cannabis in some form
• Federal law still classifies cannabis as Schedule I
• Cannabis businesses face banking restrictions and tax burdens

For consumers in Rockland County and across New York, this history matters. Understanding where these laws came from helps make sense of the current landscape: why certain products exist, why prices and availability fluctuate, and what changes might still come. Treehouse Cannabis operates in full compliance with New York's adult-use cannabis laws and tracks regulatory developments as they emerge.

Frequently Asked Questions

When did cannabis become illegal in the United States?

Cannabis was first restricted at the federal level with the Marihuana Tax Act of 1937, which effectively banned it through prohibitive taxation. Full criminalization came with the Controlled Substances Act of 1970, which classified cannabis as a Schedule I substance — the most restrictive category.

What was the reason for cannabis prohibition?

Multiple factors drove prohibition. Harry Anslinger, head of the Federal Bureau of Narcotics, ran a fear-based campaign targeting communities of color and immigrants. Sensationalist media amplified myths about cannabis-induced violence. Economic interests, including timber companies competing with hemp, also played a role. Medical arguments were secondary to political and racial motivations.

Is cannabis still a Schedule I drug?

Yes — at the federal level, cannabis remains classified as a Schedule I controlled substance under the Controlled Substances Act, defined as having a high potential for abuse and no accepted medical use. This classification persists despite decades of evolving state-level legalization and growing scientific debate.

What role did Harry Anslinger play in cannabis prohibition?

Harry Anslinger became head of the Federal Bureau of Narcotics in 1930 and built his career on anti-cannabis rhetoric after alcohol prohibition ended and his agency needed a new target. He testified before Congress, wrote inflammatory articles, and pushed for the 1937 Marihuana Tax Act that effectively ended legal cannabis in America.

How many states have legalized cannabis?

As of 2026, more than 25 states and Washington D.C. have legalized cannabis for recreational adult use, with most states permitting some form of medical cannabis. However, cannabis remains illegal under federal law, creating a complex patchwork of regulations that affects banking, research, and interstate commerce.

What happened to cannabis laws after the 1937 Marihuana Tax Act?

The Marihuana Tax Act effectively ended legal cannabis by imposing steep taxes and bureaucratic requirements that made compliance impossible. Farmers lost access to hemp, the pharmaceutical industry lost a common medicine, and personal possession became a federal crime. This set the stage for the harsher penalties and full criminalization that came with the Controlled Substances Act of 1970.

Sources

1. Wikipedia — Legal history of cannabis in the United States
2. PBS Frontline — The Doping of America
3. History.com — Why the U.S. Made Marijuana Illegal
4. NIAAA Alcohol Policy Information System — Cannabis Policy
5. U.S. Drug Enforcement Administration — Controlled Substances Act

Treehouse Cannabis is a licensed adult-use dispensary in Rockland County, New York. Must be 21+ to purchase. This content is for informational purposes only and is not medical advice.