They call the day “4/20.” It’s the one day out of the year that marijuana aficionados attest they can celebrate cannabis sativa with relative impunity. When California voters voted in November 2016 to legalize recreational use of marijuana, they believed that the state could be in for an economic boom. So far, eight states have legalized recreational marijuana, and another 29 allow for its medical use. California is recognized as the world’s largest legal market and will probably define the legality of recreational marijuana for the world.

Last year in North America, legal marijuana sales exceeded $6.6 billion and in four years that figure could triple with California expected to lead the growth. The Pew Research Center conducted a study last year that found that 57 percent of adults agree that recreational marijuana should be legalized. Supporters of Prop 64 in November were confident that legalization would shift control of the marijuana market from violent drug cartels to law-abiding citizens who will open businesses and pay taxes and, ultimately, create jobs.

The term “4/20” has a lot of background to it—some of it accurate, most of it fictional. The most credible story traces the date to Marin County circa 1971. There, five students at San Rafael High School would reportedly meet every day or so at 4:40 p.m. by the campus statue of chemist Louis Pasture to smoke a joint. Two of these students, David Reddix and Steve Capper, years later would write an article for the Huffington Post about how the group—known as the “Waldos” because they reportedly met at a wall near the statue—would say ‘4/20” to each other as code for marijuana.

One of the teens knew Phil Lesh, the bass player for the Grateful Dead. Legend has it that the band helped to popularize the term and on Dec. 28, 1990, Deadheads in Oakland handed out flyers reportedly inviting people to “smoke 4/20” on April 20 at exactly 4:20 p.m. One of these flyers found its way to Steve Bloom, a reporter with High Times magazine, and once the publication published the flyer and continued reference to the number, it became known globally for its association with marijuana.

Still, there are other theories about how the name 4/20 came about. One story goes that there are 420 active chemicals in marijuana, hence the obvious connection between the drug and the number. The Dutch Association for Legal Cannabis says there are more than 500 active ingredients in marijuana, but only about 70 or so are cannabinoids unique to the plant. Another theory suggests 4/20 is code among police officers for “marijuana smoking in progress.” Then there’s Adolf Hitler’s birthday, or even Bob Dylan’s song “Rainy Day Women No. 12 & 35” because 12 multiplied by 35 equals 420.

Today, major rallies are expected to occur across the country, particularly in California, Colorado, Washington State and in Washington, D.C. The festivities are becoming more mainstream and as a result, marijuana businesses (both medical and recreational) are looking to leverage the holiday to find more ways to sell and market their product. Essentially, while the so-called holiday varies from person to person it is reasonable to assume that some people just want to get high and have fun. Others may see the day as a moment to push for further legalization, or to celebrate legalization now that more states are adopting it and have popular opinion behind it.

While 4/20 is a nod to the hippies and flower children of the 1960s and early ‘70s, marijuana legalization may undercut that original purpose. As big businesses and corporations race to begin growing and selling marijuana, the leafy drug may lose its counterculture status. Keith Humphreys, a drug policy expert at Stanford University, believes that in time there will be more people in designer suits than wearing blue jeans smoking marijuana.

“If a corporate marijuana industry adopts 4/20, it would still be a celebrated event, but not with the same countercultural meaning,” Humphreys suggested. “People celebrated Christmas long before it became an occasion for gift buying and materialist consumption. The meaning of 4/20 is bound to be different than what it is now.”