A record number of American citizens support marijuana legalization, according to two new national polls, in a continuation of multi-year trend.

As proponents of legalization proliferate, legislatures are beginning to direct the swell of public opinion to the polls, where four states and the District of Columbia have already legalized recreational marijuana. This November, five more states will put the question of legalization before voters.

Sixty percent of those polled by Gallup this month supported legalization, similar to the 57 percent polled earlier this fall by the Pew Research Center. One decade ago, those numbers were just 35 and 32 percent, respectively, highlighting the sudden groundswell of public support for legalization in recent years.

The growth is particularly rapid among younger Americans.

"Young people under 35 have shifted the most over the last 10 years or more. That’s important," Frank Newport, the editor in chief of Gallup.com, told Yahoo News. "That’s where social change usually occurs. Older people tend to be set in their ways, and that seems to be happening here as well."

Support for legalization is highest among Millennials, with 77 percent of people in that age bracket in favor of making cannabis legal, according to Gallup, but it is also growing among other generations. Among those over the age of 55, for example, 45 percent say that pot should be legal.

This week’s Gallup poll release shows the highest rate of support for marijuana legalization ever recorded among American citizens. Although the pro-legalization movement has been growing steadily since the mid-1990s, historically, that wasn't always the trend.

Prior to the past two decades’ movement, marijuana last saw historic rates of support in the late 1970s, when 28 percent of Gallup respondents said that they were in favor. Just one decade before, the first-ever poll of public opinion on the subject found only 12 percent in favor. In the 1980s, support once again dipped, which some observers attribute to anti-drug crusades that portrayed marijuana as a gateway drug, whose use could encourage teens to experiment with other substances.

Father Richard McGowan, a professor at Boston College's Carroll School of Management, tells The Christian Science Monitor that while older Americans might not have initially supported marijuana, the aging generation is likely becoming more aware of marijuana's medicinal uses.

In part, however, spreading support may be because of the "ethics of tolerance," he has argued before: the individualistic attitude that "people think you should be able to do whatever you want as long as you don’t harm somebody else."

Those who support legalizing the drug say that the upward trend can be attributed to the increased availability of accurate information about marijuana and its potential effects.

"There is more credible information out there than ever before," Mason Tvert, the communications director of the Marijuana Policy Project, told The Washington Post. "As people learn that marijuana is not as dangerous as they were once led to believe, they tend to be supportive of taking a new approach."

Adam Rathge, a PhD candidate at Boston College who is writing his dissertation on the history of marijuana prohibition, tells the Monitor that he sees two reasons why young people are so favorable towards legalization.

Young people today grew up schools' Drug Abuse Resistance Education (D.A.R.E.) programming, which "tended to treat all drugs the same and provided a universal message that drug use was harmful and dangerous," Mr. Rathge says. "When young people grew into teenagers and entered college they encountered marijuana users who didn't seem to be the unemployed, brain-dead drop-outs caricatured to them as school children. Second, they came of age with the rise in medical marijuana."

Legalization in some states also likely played a role in increasing support, which started to grow especially quickly beginning in 2013, when Colorado and Washington state voted to make the drug legal.

According to Father McGowan, gradual acceptance nationwide creates a domino effect. McGowan, who studies the intersection of public policy and business, likens the shift to the cultural acceptance of gambling.

"When states legalized lotteries, it gave the signal to other Americans that there’s nothing wrong with gambling, that as long as it isn’t hurting you, why not let other people do it? So one state after another legalized lotteries," he says.

A similar trend is occurring with marijuana legalization, he argues. "At least 25 states have medical marijuana. Now, voters in other states are looking at them and saying, ‘Well, it isn’t hurting me. Why not?"

Some states, however, are holding back, as the Monitor has previously reported – and marijuana is still classified as a Schedule I substance by the federal government, as are cocaine and heroin. The categorization means it has "no current accepted medical use in treatment in the United States," in the eyes of the Drug Enforcement Agency.

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"We in the Commonwealth would be better watching and learning from the case study of Colorado for five or six years, rather than just two," Sen. Viriato deMacedo (R) of Massachusetts, one of nine senators who went on a fact-finding mission to the Boulder State, told the Monitor in May. The trip opened some senators' eyes to new complications, from pesticides to safety concerns over popular marijuana-infused "edibles."

"I think if people understand that this not about – 'Do we want marijuana, yes or no?' – this is about legalizing an entire industry and people competing about who has the best marijuana," Sen. deMacedo said. "It's about money, and I don't think most people have an understanding of that."