History of Medical Marijuana in the United States

The story of medical marijuana in the United States is longer, stranger, and more legally tangled than most people expect — stretching from 19th-century pharmacy shelves to a 2024 federal rescheduling proposal that's still working its way through administrative review. This page traces that arc: the major legislative turning points, the science that reshaped the conversation, and the patchwork of state programs that emerged from decades of federal prohibition. Understanding this history explains why the medical marijuana landscape looks the way it does today.

Definition and scope

Cannabis appeared in the United States Pharmacopeia (USP) from 1851 until 1942, verified as a treatment for conditions ranging from neuralgia to gout. Pharmacists dispensed it as a tincture. Physicians prescribed it. The plant was, in the clearest regulatory sense, medicine.

That status unraveled fast. The Marihuana Tax Act of 1937 effectively criminalized cannabis at the federal level by imposing transfer taxes so burdensome that legitimate medical and agricultural use collapsed. The USP delisted cannabis in 1942. Then, in 1970, the Controlled Substances Act (21 U.S.C. § 811) placed marijuana in Schedule I — the most restrictive classification, reserved for substances with "no currently accepted medical use" and high abuse potential. That classification has never been changed by Congress, though the Drug Enforcement Administration (DEA) received a formal recommendation from the Department of Health and Human Services (HHS) in 2023 to move marijuana to Schedule III (HHS letter to DEA, August 2023).

The tension between Schedule I status and active state medical programs isn't a bug in the system. It is the system — a 30-year-old structural contradiction that shapes everything from dispensary banking to patient employment rights. For a detailed breakdown of that conflict, see the regulatory context for medical marijuana.

How it works

The modern state-program era began with a single ballot measure. California's Proposition 215, passed by voters in November 1996, created the first legal framework for physician-recommended cannabis use in the United States. It was narrow — protecting patients and caregivers from state prosecution — but its passage cracked a door that 38 states (plus Washington D.C., Guam, Puerto Rico, and the U.S. Virgin Islands) have since walked through (NCSL, State Medical Cannabis Laws).

The federal government pushed back hard through the early 2000s. The Supreme Court ruled in Gonzales v. Raich (2005) that the Commerce Clause gave Congress authority to regulate even intrastate, non-commercial cannabis activity — meaning federal prosecution remained possible regardless of state law. That ruling still stands.

The pivot point came in 2009, when the Department of Justice issued the Ogden Memorandum, directing federal prosecutors to deprioritize cases against patients and caregivers in compliance with state law. The 2013 Cole Memorandum expanded that guidance to state-licensed businesses. Both memos were rescinded in January 2018 under Attorney General Jeff Sessions — reinstating prosecutorial discretion — but enforcement practice remained largely unchanged, and the 2022 Joyce Amendment to federal appropriations (H.R. 2617) continued blocking DOJ funds from being used to interfere with state medical marijuana programs.

Science was accelerating the policy conversation simultaneously. The discovery of the endocannabinoid system in the early 1990s — including the CB1 and CB2 receptor pathways — provided a biological mechanism for cannabis effects that hadn't existed when Schedule I was assigned. The FDA's approval of Epidiolex (cannabidiol) for two severe epilepsy syndromes in 2018 (FDA approval letter, June 2018) marked the first plant-derived cannabis medicine cleared through full clinical trials.

Common scenarios

State programs fall into three broad structural types:

1. Recommendation-only states — Physicians issue written certifications; the state issues patient ID cards; licensed dispensaries serve registered patients. This is the most common model, used in states including Florida, Pennsylvania, and New York.
2. Caregiver-cultivation states — Smaller or earlier-adopting states (New Mexico, Maine at various points) permitted home cultivation or designated caregiver grows before commercial dispensary networks existed.
3. Integrated medical-recreational markets — States like Colorado and California maintain distinct medical programs alongside adult-use retail, often with lower taxes, higher possession limits, or access to higher-potency products for registered patients.

The qualifying conditions attached to these programs have expanded steadily. Early programs typically verified terminal illness, cancer, HIV/AIDS, and severe seizure disorders. Chronic pain — arguably the most common reason patients enroll today — was added later, and its inclusion is not universal. A complete breakdown of conditions by state appears at qualifying conditions for medical marijuana.

Decision boundaries

The key fault lines in medical marijuana history come down to jurisdiction and evidence standard.

Federal vs. state jurisdiction: Schedule I status means no federally insured financial institution can safely serve cannabis businesses, no VA physician can recommend cannabis to veterans under VA policy, and interstate transport remains a federal crime regardless of origin and destination state law. Patients who cross state lines with their medicine enter legally ambiguous territory regardless of both states' medical status.

Pharmaceutical standard vs. state program standard: FDA-approved cannabis medicines like Epidiolex and the synthetic THC medications Marinol and Syndros (FDA, Cannabis and Cannabis-Derived Compounds) went through Phase III clinical trials with defined dosing, manufacturing standards, and labeling requirements. State medical programs operate outside that pathway entirely — patients access whole-plant products through dispensaries, with state-level testing requirements that vary by market. These are two distinct regulatory tracks that occasionally intersect but are not interchangeable.

Rescheduling vs. descheduling: The HHS recommendation to move marijuana to Schedule III would acknowledge accepted medical use and lower abuse classification, but it would not eliminate federal control or resolve the banking and interstate commerce problems. Full descheduling — removal from the Controlled Substances Act entirely — would require separate Congressional action.