Marijuana use was legal for most of human history, until the early 20th century. Between 1916 and 1931, 29 U.S. states banned the use of marijuana. The Marihuana Tax Act of 1937 essentially made cannabis illegal across the U.S. Many other countries outlawed marijuana during the first half of the century, with more nations following suit in subsequent decades.

But the tide is turning. Many countries and U.S. states have legalized the use and sale of medical marijuana. A couple of countries and a growing number of U.S. states permit recreational marijuana. This has created opportunities for investing in marijuana stocks along the way.

Where is marijuana legal now? Here's what you need to know.

Marijuana legalization in the United States

Both medical and recreational marijuana use are illegal at the federal level in the U.S. The Controlled Substances Act of 1970 placed cannabis in the most restricted category, Schedule I, which includes drugs the government deems have no accepted medical use and a high potential for abuse.

But states eventually began to push back against federal marijuana policy, beginning with a ballot initiative in California, passed in 1996, that legalized medical marijuana. Other states soon followed California's lead. Here are the U.S. states, districts, and territories that have broadly legalized either medical marijuana or recreational marijuana as of June 15, 2020:

State/District/Territory Medical or Recreational Legal? Milestones Alaska Both 1998: Voters pass Measure 8, which allows medical use of marijuana.

2014: Voters pass Ballot Measure 2, legalizing recreational marijuana. California Both 1996: Voters pass Proposition 215, legalizing medical marijuana.

2003: The Legislature passes SB 420, which protects physicians from being punished for recommending medical marijuana to patients.

2016: Voters pass Proposition 64, legalizing recreational marijuana. Colorado Both 2000: Voters pass Ballot Amendment 20 to legalize medical marijuana.

2012: Voters pass Amendment 64, legalizing recreational marijuana. District of Columbia Both 1998: Voters pass Ballot Initiative 59, which permits seriously ill patients to use medical marijuana when it is recommended by a licensed physician. However, U.S. Congress votes to prevent the initiative from being enacted.

2009: Congress reverses its blocking of D.C.'s Initiative 59.

2010: Council passes L18-2010, legalizing medical marijuana.

2014: Voters pass Initiative 71, legalizing recreational marijuana. Guam Both 2014: Voters pass Proposition 14A, legalizing medical marijuana.

2019: Legislation passes to legalize recreational marijuana. Illinois Both 2013: The Legislature passes HB 1 to allow the compassionate use of medical marijuana.

2019: The Legislature legalizes recreational marijuana. Maine Both 1999: Voters pass Question 2, a ballot initiative legalizing medical marijuana.

2009: Voters pass the Question 5 ballot initiative to create nonprofit medical cannabis dispensaries and to establish a statewide system for identification cards to protect patients who use medical marijuana from being arrested.

2010: The Legislature passes LD 1811, amending the state's medical marijuana laws to establish a medical advisory board for adding new conditions for which medical marijuana can legally be used. Massachusetts Both 2012: Voters pass the Question 3 ballot initiative, legalizing medical marijuana.

2016: Voters pass the Question 4 ballot initiative, legalizing recreational marijuana. Michigan Both 2008: Voters pass a proposal to legalize medical marijuana.

2018: Voters pass a proposal to legalize recreational marijuana. Nevada Both 2000: Voters pass Question 9 to amend the state's constitution to allow medical marijuana.

2016: Voters pass the Question 2 ballot initiative, legalizing recreational marijuana. Oregon Both 1998: State passes the Oregon Medical Marijuana Act.

2007: The Legislature passes SB 161, amending provisions and creating new provisions related to medical marijuana use.

2014: Voters pass Measure 91, legalizing recreational marijuana. Vermont Both 2004: The Legislature passes SB 76, which legalizes the use of medical marijuana for patients with specified serious illnesses.

2007: The Legislature passes SB 7, expanding the use of medical marijuana to more conditions.

2018: The Legislature passes H. 511 bill, to allow the legal use of recreational marijuana in limited quantities. Washington Both 1998: Voters pass Initiative 692, legalizing medical marijuana.

2010: The Legislature passes SB 5798, to allow authorized healthcare professionals other than physicians to recommend medical marijuana for patients.

2012: Voters approve Initiative 502, legalizing recreational marijuana. Arizona Medical 2010: Voters pass Proposition 203, legalizing medical marijuana. Arkansas Medical 2016: Voters pass Issue 6 to amend the state constitution to legalize medical marijuana. Connecticut Medical 2012: The Legislature passes bill to legalize medical marijuana. Delaware Medical 2011: The General Assembly passes SB 217, legalizing medical marijuana. Florida Medical 2016: Voters pass Amendment 2, legalizing medical marijuana. Hawaii Medical 2000: The Legislature passes SB862, legalizing the medical use of cannabis. Louisiana Medical 2016: SB271 and SB280 signed into law, allowing the medical distribution of marijuana. Maryland Medical 2014: The Legislature passes HB881, legalizing medical marijuana. Minnesota Medical 2014: The Legislature passes SF 2470, allowing the legal use of medical marijuana. Missouri Medical 2018: Voters pass Amendment 2, legalizing medical marijuana. Montana Medical 2004: Voters pass Initiative 148, allowing the legal use of medical marijuana for patients with debilitating conditions.

2011: The Legislature passes SB 423, expanding the state's medical marijuana laws. New Hampshire Medical 2013: The Legislature passes HB 573, legalizing the use of medical cannabis. New Jersey Medical 2009: The Legislature passes SB 119, legalizing medical marijuana. New Mexico Medical 2007: The Legislature passes SB 523, legalizing medical marijuana for compassionate use. New York Medical 2014: The state assembly passes A6357, legalizing medical marijuana. North Dakota Medical 2016: Voters pass Measure 5, legalizing medical marijuana. Ohio Medical 2016: The Legislature passes HB 523, legalizing medical marijuana. Oklahoma Medical 2018: Voters pass Question 788, legalizing medical marijuana. Pennsylvania Medical 2016: The Legislature passes SB 3, legalizing medical marijuana. Puerto Rico Medical 2007: General Assembly passes SB 791, allowing the legal use of medical marijuana for certain medical conditions. Rhode Island Medical 2009: The General Assembly passes SB 185, amending its medical marijuana laws to establish centers for the distribution of medical marijuana. Utah Medical 2018: The Legislature passes HB3001, legalizing medical marijuana. West Virginia Medical 2017: The Legislature passes SB 386, legalizing medical marijuana.

Global marijuana legalization

Here are the countries that have broadly legalized the use and sale of marijuana as of June 15, 2020:

Country Medical or Recreational Legal? Canada Both Uruguay Both Argentina Medical Australia Medical Barbados Medical Bermuda Medical Brazil Medical (for terminally ill patients) Chile Medical Colombia Medical Croatia Medical Cyprus Medical (for cancer patients only) Czech Republic Medical Denmark Medical Ecuador Medical Finland Medical Georgia Medical Germany Medical Ghana Medical (with THC content < 0.3%) Greece Medical Ireland Medical (under pilot program) Israel Medical Italy Medical Jamaica Medical Lebanon Medical Lithuania Medical Luxembourg Medical Malawi Medical Malta Medical Mexico Medical (with THC content < 1%) Netherlands Medical New Zealand Medical North Macedonia Medical Norway Medical Peru Medical Poland Medical Portugal Medical Saint Vincent and the Grenadines Medical San Marino Medical South Korea Medical Sri Lanka Medical Switzerland Medical Thailand Medical United Kingdom Medical Vanuatu Medical Zambia Medical Zimbabwe Medical

What's next for marijuana legalization?

More countries and states are likely to legalize medical marijuana in the coming years. Given the research, it's hard to argue that marijuana doesn't have some medical benefits.

As public support keeps increasing, it wouldn't be surprising for more countries and U.S. states to legalize recreational marijuana. The tax revenue being generated from legalized recreational marijuana could prove tempting to many governments.