A young man smokes a marijuana cigarette at a park where people gathered to mark the First Worldwide March for Regulated Marijuana in Montevideo, Uruguay, Saturday, May 3, 2014. Uruguay released its rules Friday afternoon for the legal marijuana market it is launching this year. In Uruguay, consumers must be licensed, and each purchase will be tracked to ensure they buy no more than 10 grams a week, said Mujica who along with his minister will sign the regulations on Monday, and they'll take effect on Tuesday. (AP Photo/Matilde Campodonico)

A broad new survey shows that a majority of American adults continue to support marijuana legalization in the United States, and that support appears to be growing.

The survey, released last week from online polling data company CivicScience, asked more than 450,000 U.S. adults over the last two years this question: "Would you support or oppose a law in your state that would legalize, tax, and regulate marijuana like alcohol?"

Fifty-eight percent of respondents said they support marijuana legalization -- with 39 percent saying they "strongly support" and 19 percent saying they "somewhat support" reformed marijuana laws in their states. Thirty-five percent oppose legalization of marijuana -- with 29 percent "strongly" opposing and 6 percent "somewhat" opposing laws that would regulate marijuana like alcohol. Seven percent of respondents had no opinion on the issue.

CivicScience then broke out the data from just the last three months of responses -- from May to August -- and saw an increase in support and decrease in opposition to the regulation of marijuana like alcohol. Of those who responded most recently, 61 percent said they strongly or somewhat support marijuana legalization, while only 30 percent were opposed.

Men were found to be slightly more in favor of legalization than women were, by 60 to 55 percent, according to CivicScience's survey data. Support for legalization was strongest among people ages 25-34; the only age group in which the majority of people opposed legalization was those over 65.

The question, asked between November 2012 and August 2014, was hosted on as many as 400 different websites across the U.S. Each respondent was anonymous and answered the question "just for fun," according to CivicScience.

Jennifer Sikora, a spokesperson for CivicScience, explained to The Huffington Post that although the survey was online, the company uses browser cookies to keep respondents from answering the question more than once. In order to further hedge against a person answering the same question multiple times, the question is part of a pool of more than 1,000 rotating questions on multiple websites to further decrease the possibility that a respondent might happen upon the same question again. Still, Sikora says, there is a very small percentage of respondents who do repeat the answer (after all, cookies can be deleted), but the 453,653 U.S. adults in this survey are unique.

"This huge poll is yet another indication that marijuana legalization is officially a mainstream issue," Tom Angell, chairman of Marijuana Majority, told HuffPost. "With ending prohibition polling better with voters than most elected officials do these days, it'll be really interesting to see which 2016 contenders realize that supporting marijuana reform is good politics and which still don't get it."

This isn't the first recent poll to show a majority of Americans supporting marijuana legalization. In April, a survey from Pew found that 54 percent of Americans support legalizing marijuana use, and about three-quarters of Americans told Pew that if marijuana use isn't legalized, those found in possession of small amounts of the substance should not go to jail. Just last year, Gallup found for the first time that a clear majority of Americans -- 58 percent -- say marijuana should be legalized.