One person was arrested every 49 seconds for marijuana in 2015

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A woman walks with a sign supporting legalizing marijuana during the Democratic National Convention (DNC) on July 28, 2016 in Philadelphia, Pennsylvania.

A huge number of Americans are getting arrested for marijuana-related offenses.

643,000 people were arrested for marijuana in 2015, according to crime data released by the FBI on Monday. That amounts to one person arrested for marijuana every 49 seconds.

574,000 of these arrests were for possession rather than distribution and sale, according to the FBI's data.

While the 2015 numbers are startling, marijuana arrests have actually steadily decreased since 2007, when 872,720 people were arrested. 2015 also saw the lowest total number of marijuana arrests since 1996.

However, for a plant that's already recreationally legal for adults in four states and Washington D.C., that's still a huge drain on the country's legal system.

States spent a combined $3.6 billion on enforcing marijuana possession laws alone, according to a 2013 report from The American Civil Liberties Union.

While marijuana prohibition is quite costly, legalizing and commercializing the drug could generate up to $28 billion in tax revenue.

Recent polls also show that the majority of Americans support legalizing marijuana nationwide.

"While the numbers are thankfully dropping over time, it's alarming and simply unacceptable that someone is harassed by the police just for marijuana every 49 seconds in this country," Tom Angell, the chairman of Marijuana Majority, an advocacy group told Business Insider via email. "Polls now consistently show that a growing majority of Americans supports full legalization, and it's about time more politicians and law enforcement caught up."

In November, recreational marijuana is set to hit the ballot in five states, including Massachusetts, Maine, Arizona, California, and Nevada.

"Our movement is set to more than double the number of states with legalization this November, and we won't stop pushing until the day when no one is put into handcuffs or cages just because they choose to consume cannabis," Angell said.