Marijuana legalization is spreading around the US.

Since 2012, 15 states and Washington, DC, have legalized marijuana for adults over the age of 21. And 36 states have legalized medical marijuana — meaning that a majority of Americans have access to marijuana, whether medically or recreationally.

New York became the latest state to embrace cannabis when Gov. Andrew Cuomo signed a bill legalizing marijuana on March 31. His move came shortly after New Jersey Gov. Phil Murphy signed legislation officially legalizing marijuana in his state.

New Jersey was one of four states, along with Arizona, Montana, and South Dakota, where voters backed legalizing recreational cannabis in November. Voters in Mississippi approved the creation of a medical cannabis program.

Virginia and New Mexico are also close to legalizing recreational cannabis.

Some states that passed medical or recreational legislation through ballot measures have yet to iron out the details. For that reason Insider does not include South Dakota or Mississippi in our tally of markets where the substance is legal. Both states have faced legislative opposition to rolling out their programs.

Though Canada legalized marijuana federally in 2018, the US has not followed suit, forcing states to chart their own courses. As it stands, marijuana is still considered an illegal Schedule I drug by the US federal government.

Joe Biden's victory in the presidential election and the Democratic party's control of Congress could give marijuana a bigger boost in the US. In March, the SAFE Banking Act — a bill that would help cannabis businesses access banks — was reintroduced in both chambers of Congress.

Biden has said he would support federal decriminalization of the drug, and Senate Majority Leader Chuck Schumer has said that marijuana reform will be a priority for the Senate this year.

Alaska

A cannabis-testing laboratory in Santa Ana, California.

Adults 21 and over can light up in Alaska. In 2015, the northernmost US state made it legal for residents to use, possess, and transport up to an ounce of marijuana — roughly a sandwich bag full — for recreational use. The first pot shop opened for business in 2016.

Alaska has pounced on the opportunity to make its recreational-pot shops a destination for tourists. More than 2 million people visit Alaska annually and spend $2 billion.

Arizona

Arizona in 2020 voted to legalize cannabis for all adults over the age of 21.

The measure had support from almost 60% of Arizona voters, according to Decision Desk HQ.

The ballot measure was backed by a number of cannabis giants, including Curaleaf, Cresco, and Harvest Enterprises.

The Arizona Department of Health Services began accepting applications for adult-use licenses on January 19. Approvals were issued just three days later on January 22. Sales began immediately.

Arizona rolled out adult-use sales faster than any other state that voted to pass recreational cannabis in the November elections. Companies already operating in the state's medical market had a first crack at recreational customers.

California

In 1996, California became the first state to legalize medical marijuana. California became even more pot-friendly in 2016 when it made it legal to use and carry up to 1 ounce of marijuana.

The law also permits adults 21 and over to buy up to 8 grams of marijuana concentrates, which are found in edibles, and grow no more than six marijuana plants per household.

Colorado

In Colorado, there are more marijuana dispensaries than Starbucks and McDonald's combined. The state joined Washington in becoming the first two states to fully legalize the drug in 2012.

Residents and tourists over the age of 21 can buy up to 1 ounce of marijuana or 8 grams of concentrates. Some Colorado counties and cities have passed more restrictive laws.

Illinois

Illinois Gov. J.B. Pritzker.

Illinois lawmakers in June 2019 passed a bill that legalized the possession and commercial sale of marijuana in the state starting on January 1, 2020.

Gov. J.B. Pritzker, who made marijuana legalization a core component of his campaign for the governor's office, signed the bill into law.

Illinois is the one of the few states to legalize marijuana sales through a state legislature, rather than a ballot initiative.

Maine

Harvested cannabis plants at Hexo Corp.'s facilities in Gatineau, Quebec, on September 26, 2018.

A ballot initiative in 2016 gave Maine residents the right to possess up to 2.5 ounces of marijuana, more than double the limit in most other states.

Massachusetts

Massachusetts was the first state on the East Coast to legalize marijuana after voters approved the measure in 2016.

Marijuana dispensaries opened their doors to consumers in November 2018. Adults over the age of 21 can purchase up to 1 ounce of marijuana but cannot consume it in public.

Michigan

 The Far West Holistic Center dispensary on November 7, 2018, in Detroit. 

The law is more permissive than other states with legal marijuana: Most allow residents to possess only up to 1 ounce at a time.

Montana

A CPlant employee organizes a box of hemp for export at the company's farm on the outskirts of Tala, Uruguay, Thursday, Aug. 13, 2020.

Montana in 2020 voted to legalize recreational marijuana for adults 21 and over.

Montana residents are officially allowed to use marijuana as of January 1, 2021. A year later, the state will begin to open up applications for dispensaries.

New Jersey

New Jersey in 2020 voted to legalize recreational marijuana for adults 21 and older, opening a market that could near $1 billion.

In February, Gov. Phil Murphy signed the legalization legislation, after months of back-and-forth arguments about criminal penalties for minors possessing marijuana and the proper way to set up a licensing framework for cannabis sales in the state, among other details. Sales of cannabis for adult use could start in the second half of this year, analysts at Cowen said.

New York

After two failed attempts to legalize adult-use cannabis in New York, the state finally passed recreational marijuana on March 31, 2021.

Though New Yorkers are now able to possess and smoke cannabis legally in the state, sales aren't expected to begin for at least a year.

Andrew Carter, an analyst at Stifel, said he expects recreational cannabis sales to begin in late 2022. Analysts from Cantor Fitzgerald and Stifel estimated that New York could become a $5 billion cannabis market by 2025.

Nevada

The Essence cannabis dispensary on July 1, 2017, in Las Vegas.

Residents and tourists who are 21 and over can buy 1 ounce of marijuana or one-eighth of an ounce of edibles or concentrates in Nevada.

There's bad news if you want to grow your own bud, though. Nevada residents must live 25 miles outside the nearest dispensary to be eligible for a grower's license.

Oregon

Oregon legalized marijuana in 2015, and sales in the state started October 1 of that year.

South Dakota

A team member of Aurora Cannabis works in the grow room at Aurora Sky cannabis growing greenhouse in Alberta, Canada, in this 2018 handout image.

South Dakota in 2020 voted to legalize both medical and recreational cannabis, the first time a state has voted in favor of both at the same time.

State lawmakers have until April 2022 to create rules around cannabis, including regulations around dispensaries.

Vermont

Vermont became the first state to legalize marijuana through the legislature, rather than a ballot initiative, when Republic Gov. Phil Scott signed a bill into law in January 2018.

Adults in the Green Mountain State can carry up to 1 ounce of marijuana and grow no more than two plants for recreational use. The law went into effect in July 2018. But it was limited in scope. It didn't establish a legal market for the production and sale of the drug.

In 2020, the state legislature passed a bill that would allow for adult-use sales in the state. All localities must opt-in to allow for dispensaries, however. Sales are expected in 2022.

Washington

A medical-marijuana plantation on March 21, 2017.

Marijuana was legalized for recreational use in Washington in 2012.

The state allows people to carry up to 1 ounce of marijuana, but they must use the drug for medicinal purposes to be eligible for a grower's license.

Washington, DC

Residents in the nation's capital voted overwhelmingly to legalize marijuana for adult use in November 2014.

The bill took effect in 2015, allowing people to possess 2 ounces or less of marijuana and "gift" up to an ounce, if neither money nor goods or services are exchanged.