(CNN) -- In an office run from his Massachusetts home, William Downing is part of a burgeoning national pro-pot movement emboldened by the approval of recreational marijuana laws in Colorado and Washington.
"I'm a believer, as The Monkees said," Downing said, a reference to a pop-rock band from an era when the thought of marijuana legalization was all but unimaginable.
Downing is treasurer of the group Bay State Repeal in Massachusetts, which already has dozens of medical marijuana dispensaries and decriminalized possession of small amounts of the drug. Now, Downing and others are pushing for full legalization of recreational marijuana by making the case to state voters during a proposed 2016 ballot initiative.
"The essence of what's happening is that people are getting educated," Downing said. "People are learning. The rest of the nation is finding out that they have been lied to about cannabis by their government for many decades."
This week, Colorado became the first state to sell marijuana for recreational use. Hundreds of buyers waited in line for hours to be a part of opening-day history. Sales were brisk.
Now, Colorado's historic legalization policy is being touted as a springboard for the other states.
In 2012, Colorado voters approved the sale of recreational marijuana, as did voters in Washington state. But Colorado is the first to have the pot shops up and running under regulations recently established by state and local governments. Colorado voters' approval in effect amended the state's constitution to allow for the retail sale of recreational pot. The state already allowed medical marijuana.
The entire state is not implementing the law, however. A community can decide not to allow the shops, and in fact, most areas of the state have not, including communities such as Greeley and Colorado Springs.
In November, Portland, Maine, followed Washington and Colorado's lead and legalized recreational use of the drug, while the Michigan cities of Lansing, Jackson and Ferndale resoundingly voted to let people older than 21 possess an ounce of marijuana on private property.
"We're going to set an example for the rest of the nation and the rest of the world," said Mason Tvert of the Marijuana Policy Project, the Washington, D.C.-based group that was the largest financial backer of the Colorado effort.
Tvert challenged media accounts that described Colorado's new pot law as an experiment.
"In fact, the experiment was marijuana prohibition, and that experiment failed," he said.
Advocates are pushing for recreational marijuana laws in Alaska, which could become the third state with such laws, Tvert said. And a campaign could start in Oregon this year or in 2016. In addition, pro-recreational marijuana Initiatives are expected in six other states in 2016: Arizona, California, Maine, Massachusetts, Montana and Nevada, according to Tvert.
Public opinion on legalization has changed drastically since the 1960s. There has been an unprecedented spike in approval ratings in the last year, reaching 58%, according to a recent Gallup Poll. The number marks a 10% increase since Colorado and Washington voted to legalize pot, "and the legal momentum shows no sign of abating," according to Gallup.
Opponents of marijuana legalization say there are serious health consequences, and argue the drug is often a gateway to more harmful, addictive substances.
In addition to Colorado and Washington, 18 otherstates and the District of Columbia allow some legal use of marijuana, primarily for medicinal purposes.
In Massachusetts, Downing and other activists hope to follow Colorado's lead in the next two years.
Massachusetts voters have twice supported ballot measures aimed at easing restrictions on marijuana.
In 2008, Massachusetts voters approved a ballot question decriminalizing possession of up to an ounce of pot, making it instead a civil offense punishable by a $100 fine. In 2012, Massachusetts overwhelmingly approved a ballot question allowing for up to 35 medical marijuana dispensaries around the state.
Pro-marijuana initiatives sprouting nationwide are more than a sign of a change in political attitude, Downing said.
"The momentum has to do with an understanding that cannabis is a far safer medicine and recreational substance," he said.
This follows Uruguay being the first nation to legalise about a month ago from memory