"What's driving this growth in support is an increase in information about issue," said Mason Tvert, communications director for the Marijuana Policy Project in Denver. "More information is available now than ever before; it's talked about more than ever before and more support grows for ending the prohibition."
"People are recognizing that marijuana is less harmful than alcohol and its prohibition has been just as big a failure as alcohol's prohibition," he said.
Colorado and Washington state voters decided to allow recreational use of marijuana by adults. In fact, the first-ever marijuana retail license was issued in Central City, Thursday. The recipient of the local license, Annie's, which currently operates as a medical marijuana center, still must receive its state license.
There's polling to back up greater acceptance of marijuana. A Gallup poll in October found Americans who believe marijuana should remain illegal were in the minority, a first for the Princeton, N.J., polling agency.
A clear majority of the country -- 58 percent -- answered in the affirmative when asked, "Do you think the use of marijuana should be made legal, not?" The percentage who said marijuana use should be legal represented a 10 percentage-point increase since last year, Gallup said.
A Pew Research Center survey of polling data indicated an aggregate 52 percent of American adults say the use of marijuana should be made legal, while 45 percent say it should not.
The Internet has provided a lot of information about marijuana that was difficult to access decades earlier, Tvert said.
The watershed, though, was when California approved marijuana for medical use in 1996.
"As a result, lots of people were hearing more about medical marijuana and laws were passed in more states," Tvert said.
Also, he said, Attorney General Eric Holder Jr. said in August the Justice Department would not challenge the statutes in Colorado and Washington state legalizing marijuana for recreational use or the laws permitting medical marijuana in 20 other states plus the District of Columbia.
"For the first time in history, states have the right to regulate marijuana cultivation and sales as long as they're addressing federal interests," Tvert said.
At least three bills have been introduced in the U.S. House this year that would regulate, not prohibit, marijuana in some fashion.
Rep. Dana Rohrabacher, R-Calif., sponsored the "Respect State Marijuana Laws Act of 2013," which would prevent the federal government from prosecuting state residents whose possession of marijuana is in accord with state law. The bill would legalize marijuana at the federal level to the extent it is legal at the state level.
Besides being a signatory on Rohrabacher's bill, Rep. Jared Polis, D-Colo., introduced the "End Federal Marijuana Prohibition Act of 2013," which would remove marijuana from Schedule I of the Controlled Substances Act, placing its regulation under a revamped Bureau of Alcohol, Tobacco, Marijuana, Firearms and Explosives.
Reps. Earl Blumenauer, D-Ore., also a co-sponsor of the Rohrabacher initiative, introduced the "Marijuana Tax Equity Act," which would establish a federal excise tax for marijuana sales, similar to the so-called sin tax on alcohol.
"We need to see laws change at the federal level, but states traditionally have been able to decide how to handle these types of issues, just like with alcohol," Tvert said, noting that there were hundreds of marijuana production and distribution entities regulated in states where its use is permitted.
In Colorado, voters recently passed hefty taxes on recreational marijuana to pay for regulating marijuana shops and school construction.
Cities in Maine and Michigan in recent elections voted to legalize adult possession of marijuana, NBC News reported.
But there's a caveat: It is still illegal under federal and state laws.
In Portland, Maine, for example, an adult can have some marijuana, but it's illegal for marijuana to be sold or smoked publicly.
Voters in Lansing, Mich., too, OK'd a ballot measure on marijuana possession by adults. Lansing was one of three cities in Michigan -- a medical marijuana state -- that approved such a measure.
"This was a symbolic change," Lansing Police Capt. Daryl Green told NBC News, because it's still illegal under state and federal laws.
But a more favorable or accepting view toward marijuana is viewed as dangerous in some corners.
"The issue is we are on the brink of creating the big tobacco of our time which would be called big marijuana," said Kevin Sabet, director of the Drug Policy Institute and assistant professor at the University Florida College of Medicine.
On his website, Sabet, who worked in three presidential administrations on drug policy issues, said existing drug policy leaves something to be desired -- but it should be fixed, not ditched. He also notes that what seems like a good idea now may have unintended bad results later.
Also, smoked marijuana isn't a medicine, Sabet argues, but marijuana in a pill or other form that isolates its components can be.
"Today we have two medications based on these components," he said, "and in the future we might have more."
Advocates on both sides of the issue are watching Colorado and Washington, saying the stakes are high, Pew's Stateline reported.
"Reformers look at these two states as literally laboratories," said Allen St. Pierre, executive director of NORML, a group that backs marijuana legalization.
If all things go well, he said, this is "largely the beginning of the end of cannabis prohibition."
Countering St. Pierre's argument is David Evans of the Drug Free America Foundation, which opposes legalization.
"I don't accept that marijuana legalization is inevitable," Evans told Stateline. "The states that have legalized it are going to serve as an example of what not to do."
Looking ahead, the Marijuana Policy Project will focus on several states considering either medical marijuana initiatives or adult recreational proposals, Tvert said.
"There's more movement than ever before as states are re-examining their marijuana laws," he said.