Ballot measures to legalize recreational marijuana for adults were headed for enactment in California and Massachusetts on Tuesday, while voters in Florida and two smaller states appeared to have approved initiatives permitting medical use of cannabis.
California and Massachusetts would become the fifth and sixth states allowing people aged 21 and over to use marijuana for the sheer pleasure of its intoxicating effects, extending legalization to the entire U.S. Pacific Coast and its first toehold in New England.
The Marijuana Policy Project, the nation's leading organization supporting liberalization of cannabis laws, declared victory for the measures to legalize recreational pot in California and Massachusetts.
The group based its assertions on the projections of a number of major news outlets, including the Associated Press, the Los Angeles Times, the Boston Globe, NBC and CBS, spokesman Mason Tvert said.
Likewise, the organization said medical marijuana measures had won approval in Florida, North Dakota and Arkansas.
The outcome was less certain for recreational marijuana initiatives in Maine, Arizona and Nevada, and for a medical cannabis measures in Montana.
Recreational marijuana has previously been legalized by voters in four Western states - Colorado, Washington, Oregon and Alaska - and the District of Columbia.
Before Tuesday, 25 states had already legalized cannabis in some way, whether for medical or recreational uses, or both.
Marijuana remains classified as an illegal narcotic under U.S. federal law, however.
Approval by California alone, the most populous U.S. state with 39 million people, would put nearly a fifth of all Americans in jurisdictions where recreational marijuana is legal, according to U.S. Census figures.
California was the first U.S. state to legalize medical marijuana, doing so with a ballot measure enacted in 1996.
The new measure was spearheaded by a coalition of supporters that included Democratic Lieutenant Governor Gavin Newsom and billionaire high-tech entrepreneur Sean Parker.
Proposition 64, as it is formally known, would allow adults to possess and use as much as an ounce of pot for private, recreational use and permit personal cultivation of as many as six cannabis plants.
It also would establish a system to license, regulate and tax sales of marijuana, while allowing city governments to exercise local control over commercial distribution within their borders.
California voters defeated a similar initiative in 2010, but public opinion polls show attitudes have since shifted.
Opponents of liberalized marijuana laws have argued that such measures carry major public safety risks and would make pot more accessible to youngsters.
Experts say the latest initiatives include more sophisticated regulatory mechanisms aimed at keeping cannabis away from children and banning the involvement of criminal gangs and drug cartels.
They also point to the potential for hundreds of millions in additional state tax revenue from pot sales and billions in economic activity.
Investors new to the sector said they are eager for a piece of a recreational marijuana market that by some estimates will reach $50 billion over the next decade.
"It's changed in the minds of these voters from being like cocaine to being like beer," said University of Southern California political scientist John Matsusaka.
Legalization by even a few of the states where measures are on the ballot could prod the federal government, which still classifies marijuana in the same category as heroin, to begin rethinking its laws and policies, Matsusaka said.