For as long as hip-hop has existed, it has reflected the politics of its community. The prison system has shaped life in Black America, so rap has had no choice but to engage in the ongoing battle for criminal-justice reform. “At the same time that an art form created by African American and Latino men dominates popular culture, African American and Latino men dominate American prisons,” wrote Georgetown professor Paul Butler in the Stanford Law Review. “Unsurprisingly then, justice—especially criminal justice—has been a preoccupation of the hip-hop nation.”

The statistics speak for themselves. One in three black men go to prison in their lifetime, according to the Bureau of Justice Statistics, and studies show that black women are three times more likely than white women to be incarcerated. Black students are arrested more often than their white classmates, have higher incarceration rates, and are sentenced far more harshly (often as adults). Though people of color are no more likely to sell drugs or use drugs, they’re more likely to be arrested for those crimes. Black offenders receive longer sentences than white offenders when convicted for the same crimes. The penal system punishes blackness.

Rappers have responded to this reality regularly, with songs that paint harrowing pictures of life on the inside. Public Enemy’s “Black Steel in the Hour of Chaos” captured a jailbreak in action, serving as a release of pent-up frustrations about the over-policing of American ghettos. Lifers Group’s “Belly of the Beast,” which reveals how the system dehumanizes its captives, was literally recorded in a prison by inmates. Lil Wayne, who spent eight months in prison back in 2010, addressed drug sentencing and incarceration rates head-on with Tha Carter III’s “Dontgetit.” And Meek Mill, who was sentenced harshly last week for violating his probation, wrote about how the prison-industrial complex creates a revolving door of repeat offenders on “Young Black America” earlier this year. The song now feels autobiographical.

Of course, hip-hop has fought these injustices beyond mere verse. In 1988, Public Enemy performed at New York City’s Rikers Island, both to reach prisoners on the inside and to send a message to folks on the outside. In 1994, when a 22-year-old rapper named Errol James was called to testify before the Senate about the damaging effects of rap lyrics, he instead drew their attention to Bill Clinton’s pending crime bill, which called for harsher sentencing and more prisons (and all but created incentives for filling them). In 1999, Van Jones, then a civil rights organizer in San Francisco (and now a CNN pundit), started throwing rap shows with other local activists. Emcees performed in truck flatbeds to oppose California’s Proposition 21, an initiative that increased punishment for crimes committed by young people, often charging them as adults or removing the protections afforded to minors. In 2000, Black Star and Los Angeles hip-hop ensemble Ozomatli headlined one such benefit concert in Santa Cruz, and though Prop 21 passed statewide, the measure was defeated in the Bay Area.

Recently, there has been another push for prison reform by those in the rap community. Def Jam cofounder Russell Simmons has partnered with Jones on Cut50, a bipartisan effort to cut the prison population in half over the next decade. In 2013, longtime Roots affiliate Dice Raw released a mini-doc on mass incarceration called Jimmy’s Back, the rap interpretation of Michelle Alexander’s book, The New Jim Crow. Nas sat down with activist Angela Davis at a 2014 event to discuss the prison-industrial complex and sold black Santa sweaters to raise money for the Center for Court Innovation, a nonprofit seeking to reduce incarceration. Even Waka Flocka Flame, the jokester who once celebrated 4/20 by announcing a fake presidential campaign, went on “The Nightly Show” for a panel debate over Clinton’s 1994 crime bill, now overwhelmingly viewed as a mistake.