Eric Holder announced his resignation at the White House on September 25th. Photograph by Win McNamee / Getty

The other day, I attended an investiture ceremony for Robert Wilkins, an African-American judge recently appointed to the U.S. Court of Appeals for the District of Columbia Circuit. At the ceremony, the Harvard Law Professor Ken Mack spoke about some of Judge Wilkins’s forebears—in particular, Robert Terrell, the first black federal judge, appointed in 1910, and William Henry Hastie, the first black federal Court of Appeals judge, appointed in 1949. These men served under, and swore to enforce, a federal Constitution that blessed racial segregation as “separate but equal.” As Mack said, Judges Terrell and Hastie had to be fair and just in a world that was neither fair nor just to them. Mack did not say but plainly implied that black judges today face a similar challenge—different in degree, to be sure, but not in kind. Wilkins himself first came to prominence when, in 1993, he filed the first successful legal challenge to racial profiling. He was the plaintiff in that suit, not the lawyer. Maryland state troopers had illegally stopped him and his family as they drove home from a funeral.

Eric Holder, who announced his intention to resign today, is the nation’s first black Attorney General. That we have a black Attorney General, appointed by a black President, is an undeniable sign of progress in our long history of troubled race relations. But as a black man, Holder has, with Wilkins, inherited Terrell and Hastie’s challenge. He sits atop a criminal-justice system renowned for its harsh sentences, mass incarceration, and, most disturbingly, disproportionate burdens on African-Americans. In fact, no aspect of American life has appeared more resistant to racial progress than the criminal-justice system. In the nineteen-fifties, when segregation was legal, African-Americans made up about thirty per cent of the prison population; today, they make up thirty-seven per cent, and that population has increased exponentially. Since 1980, the number of federal prisoners has grown eight hundred per cent. On any given day, one out of every ten black men in their thirties is in prison or jail.

In 2009, Eric Holder, who as a law student interned at the N.A.A.C.P. Legal Defense and Educational Fund, took charge of our criminal-justice system. He succeeded a long string of attorneys general who proudly proclaimed that they were tougher on crime than their predecessors, and he broke with that tradition. He reversed a policy, instituted by John Ashcroft, that required federal prosecutors to charge defendants with the most serious criminal charges available. He convinced the U.S. Sentencing Commission to reduce sentencing guidelines for low-level drug offenders, supported a bipartisan effort in Congress to reduce many mandatory minimum sentences, and directed prosecutors not to charge low-level drug offenders with crimes that carry severe mandatory minimum sentences. He urged states, where the bulk of criminal law enforcement takes place, to follow his lead in reducing reliance on incarceration, and used federal funding to support their doing so. He has funded alternatives to incarceration, such as drug courts, and Justice Reinvestment, a program in which states seek to release nonviolent offenders and invest the savings in impoverished communities.

These initiatives are making a difference. Earlier this week, Holder announced that, for the first time in thirty-three years, the federal prison population has dropped. It fell by forty-eight hundred inmates this past year and is projected to fall by another twelve thousand in the next two years. That’s the equivalent of closing six federal prisons. The nation’s over-all incarceration rate has fallen by about ten per cent since Holder took office. Holder cannot take full credit for that shift—much of it has happened at the state level, most dramatically in California, New York, and New Jersey—but his plea for sentencing reform appears to have been heard.

Holder has also brought much-needed attention to the ways in which criminal law is enforced on a daily basis. He was the Administration’s point person in responding to the crisis in Ferguson, when a white police officer shot and killed an unarmed black man, and has announced a Justice Department civil-rights investigation into Ferguson’s policing practices. Under his tenure, the department has investigated some twenty cities for systemic civil-rights abuses in policing, and is enforcing twelve agreements designed to alter practices in those cities. He has ordered federal agents to videotape all interrogations, to reduce the likelihood that police will coerce confessions, especially from the most vulnerable. He is reportedly about to issue a more comprehensive ban on racial profiling by federal agents. And he has supported two lawsuits, in New York and Washington, challenging the adequacy of indigent criminal defense. There are limits to his reform efforts, to be sure; most notably, he has continued the troubling practice of using informants to single out and entrap Muslim-Americans in invented terrorist plots. But no one in government has done more to reduce the racial injustices that pervade law enforcement on a daily basis.

Early in his term, Holder got a lot of flak for saying, in a speech on black history, that we were “a nation of cowards” for not confronting our racist legacy. Perhaps he could have chosen better words, but I suspect the sharp reactions were more a response to the truth he had articulated. We have a long way to go if we are ever to bring the criminal-justice system into line with its promise of equality before the law. Many will remember Holder for his about-face on trying Khalid Sheikh Mohammed in criminal court in Manhattan, or his run-ins with Congress over a gun-running investigation. But those were blips on the horizon. Holder’s real legacy lies in his refusal to be a coward on matters of race, and his courage in using the power and influence of his office to press the arc of our criminal law a little closer toward justice.