Jolene Forman is a staff attorney at the Drug Policy Alliance. Suchitra Rajagopalan is a research coordinator at the Drug Policy Alliance. The views expressed in this commentary are their own.

(CNN) April 20 is a day of celebration for marijuana enthusiasts. The origin of 420 dates back to the early 1970s, when 4:20 p.m. marked the time that high school students in Marin County, just north of San Francisco, would regularly meet to consume marijuana. As people across the United States light up to mark the occasion, it is important to reflect on the ongoing legacy of marijuana criminalization and its widespread impact on black and brown communities.

Marijuana prohibition started in the 1920s at the state and local level in the southwestern United States. Despite widespread use by white people, both then and now, prohibition was driven by xenophobia and racism toward Mexican immigrants working as farmworkers. The term "marijuana" came into use as anti-cannabis factions sought to associate the substance with Mexicans, who by the early 1920s were caricatured as using marijuana to gain superhuman strength to commit acts of violence.

By the 1930s, Harry Anslinger , the godfather of modern drug prohibition, connected marijuana use to black jazz musicians and campaigned to prohibit marijuana nationally. He succeeded in 1937 with the passage of the Marijuana Tax Act. This racist attitude carried over to the modern-day war on drugs, first declared by Richard Nixon in 1971. John Ehrlichman, one of Nixon's former chief aids, confirmed that the drug war was intended to marginalize anti-war protesters and black people. Nixon achieved his goal using drug war tactics to target black communities.

According to a 2013 study from the ACLU, a black person in the United States is nearly four times more likely than a white person to be arrested for marijuana possession, despite similar rates of use.

Today, support for marijuana legalization is at an all-time high , with nearly two-thirds of the public now in favor. Nine states and Washington, D.C., have legalized marijuana for adult use, and many more states like New Jersey, New York and New Mexico could join them in the coming years. And a new report suggests the cognitive impairments associated with marijuana use in young people have been overstated and any potential impacts are not detectible after 72 hours of abstinence.

Just last Friday, Sen. Cory Gardner of Colorado announced that he has persuaded President Donald Trump, a fellow Republican, to protect states with legal marijuana from federal interference.

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The evidence is clear that marijuana legalization is working. States that have legalized are experiencing dramatic declines in marijuana arrests, preventing thousands of people each year from entering the criminal justice system for conduct that a majority of Americans think should be legal. At the same time, these states are filling their coffers with millions of dollars in new tax revenues.

Even though we've made enormous progress since the "reefer madness" days of the 1930s, we shouldn't pat ourselves on the back just yet. We still have a long way to go. We must learn from the racist animus that first led to marijuana prohibition in the United States and from the racially biased manner in which marijuana prohibition has been enforced.

The question is increasingly no longer whether to legalize marijuana, but rather how. Going forward, it is imperative that we write legalization laws -- and amend laws in states that have already legalized -- that are designed to repair these harms. This includes provisions that remove past marijuana convictions from criminal records, invest marijuana tax revenues in the communities most harmed by the war on drugs, and ensure an equitable marijuana market.

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Some states are doing just this. In California and Oregon , thousands of people can now reduce or clear past marijuana convictions. This protects people from the devastating consequences of a criminal conviction, including barriers to employment, education, housing, and public benefits. California and Massachusetts are also reinvesting marijuana tax revenues in the communities most harmed by the drug war.

So, this 420, look beyond just legalizing it. Marijuana legalization isn't -- and shouldn't be -- simply about greater access to marijuana. We must center the people who have been most harmed by decades of racialized drug policies. If we don't, marijuana legalization won't fulfill its potential to repair the devastation that mass criminalization has wrought on black and brown communities.