Millions of voters across the United States are considering measures to roll back longstanding restrictions on marijuana this Election Day.

By the end of Tuesday night, five more states could fully legalize weed, which would put nearly one-quarter of the nation’s population in areas that have rejected prohibition and decided to tax and regulate the plant. An additional four states are voting on whether to legalize marijuana for medical use. If approved, pot would become legal in some form in 29 states and Washington D.C.

Marijuana policy reformers say this could be a watershed moment for their movement.

“Nov. 8 is the most important day in the history of the marijuana legalization movement,” Tom Angell, chairman of drug policy reform group Marijuana Majority, told The Huffington Post. “The stakes couldn’t be higher. Big wins will dramatically accelerate our push to finally end federal marijuana prohibition, perhaps as soon as 2017. But on the other hand, huge losses could interrupt the momentum we’ve been building for the last several years.”

Nov. 8 is the most important day in the history of the marijuana legalization movement. Tom Angell, chairman of Marijuana Majority

The federal government still considers marijuana to be among the “most dangerous” drugs, alongside heroin and LSD, and argues that it has no “current accepted medical use.” But as the marijuana industry grows and as legalization spreads across the country, the movement’s increased political clout could help chip away at the federal ban.

While the measures proposed in each of these states are different, they’ll produce similar outcomes if approved. In states considering recreational measures, voters are deciding whether the possession, cultivation, use and sale of marijuana should be legal for adults 21 and over. In states considering medical measures, they’re voting to legalize marijuana only for qualifying patients.

The following states will vote on marijuana on Tuesday. We’ll keep this story updated throughout the election as results come in.

Recreational Marijuana Measures

Arizona ― FAILED

Medical marijuana has been legal in Arizona since 2010, but the push for broader legalization has been seen as one of the marijuana movement’s toughest battles. For months, polls in the state have shown voters largely split on Proposition 205, with two of the most recent polls suggesting a very slim lead for voters in favor of legalization.

California ― PASSED

With the sixth-largest economy in the world and about 40 million residents, the marijuana legalization movement has held up California as one of its biggest prizes. It was the first state to establish a legal medical marijuana program about 20 years ago, and since then, about two dozen states have followed.

In 2010, the state had the opportunity to become the first state to legalize recreational marijuana, but voters ultimately rejected that ballot initiative.

For most of 2016, polls found high support for Proposition 64, with recent polls hovering at just below 60 percent in favor of allowing California to join the ranks of Colorado, the District of Columbia, and three other Pacific states ―Washington, Oregon and Alaska ― in legalizing marijuana for recreational purposes.

Maine ― PASSED

Maine has been a leader on marijuana policy for decades, and has been in a good position to roll back prohibition on the East Coast. In 1976, the state legislature voted to decriminalize possession of small amounts of weed, and in 1999, voters approved marijuana for medical use.

The latest polling on Question 1, a measure to legalize retail sales and recreational use statewide, placed support at around 50 percent, with nearly 10 percent of likely voters still undecided.

Massachusetts ― PASSED

The latest polls showed growing support for a measure to legalize marijuana in Massachusetts, leading advocates to see it as one of the most likely states to do so.

More than 60 percent of likely voters supported Question 4, according to one recent survey, with 34 percent opposed. Voters in Massachusetts previously approved medical marijuana in 2012 by a similar margin, four years after a successful 2008 effort to decriminalize possession of small amounts of weed.

Nevada ― PASSED

Recent Nevada polls showed support for Question 2 hovering around 50 percent, making it more of a nail-biter for proponents of marijuana legalization. Supporters of the measure include multiple Democratic state lawmakers and some unions, while opponents include a group of Republican state lawmakers.

Las Vegas casino billionaire Sheldon Adelson almost single-handedly funded the opposition campaign, giving it over $3 million, or roughly 97 percent of the total money the campaign raised, according to the Adelson-owned Las Vegas Review-Journal.

Medical Marijuana Measures

REUTERS/Mike Segar Missy Miller holds her epileptic son Oliver in their home at Atlantic Beach, New York, on Jan. 7, 2014. Oliver suffered a brain stem injury in utero and now, at 14, has hundreds of seizures a day. His family pinned their hopes on a strain of marijuana developed in Colorado that has helped children with similar conditions.

Arkansas ― PASSED

The latest polling on Issue 6, a measure to bring medical marijuana to deep-red Arkansas and the South on Election Day, showed support at around 50 percent ― further complicated by an aggressive opposition campaign and controversy surrounding a separate ballot initiative on medical marijuana.

Florida ― PASSED

Recent polling showed Floridians likely approve medical marijuana on Tuesday, leading to hopes that it could become the first state in the South to legalize weed for any purpose (polls close earlier in Florida than in Arkansas). One survey conducted in late October showed support for the state’s Amendment 2 at over 70 percent.

Florida’s campaign for medical marijuana attracted a number of high-profile supporters hoping the state’s voters would do what they failed to do in 2014, when they rejected a similar measure. But anti-drug groups and donors ― including Adelson, who donated $1,500,000 to oppose Amendment 2 ― were intent on pushing back against the apparent momentum.

Montana ― PASSED

Montana first legalized medical marijuana back in 2004, but five years ago, state lawmakers severely gutted that medical marijuana program, prompting a dramatic decline in medical marijuana providers for state-registered patients.

Some polling suggested a lack of support for Initiative 182, a measure to repeal limitations installed by state lawmakers and establish a robust program in the state once again.

North Dakota ― PASSED

Prior to Tuesday, there wasn’t any recent polling available on North Dakota’s Measure 5. In 2014, 47 percent of voters said they supported the legalization of medical marijuana, though they hadn’t gotten the chance to vote on it until this election.

HUFFPOST READERS: What’s happening in your state or district? The Huffington Post wants to know about all the campaign ads, mailers, robocalls, candidate appearances and other interesting campaign news happening by you. Email any tips, videos, audio files or photos to scoops@huffingtonpost.com.