Exactly 150 years ago this month, three days of riots in Memphis, Tennessee, left nearly 50 dead, scores more injured, over 90 buildings wrecked, and black residents scattered and terrified. The unrest started with a rumor of black-on-white crime: Black soldiers stationed at Fort Pickering on the city’s south bluffs had allegedly killed white policemen attempting to arrest an African American soldier. Less than a month earlier, the United States Congress had passed the Civil Rights Act of 1866, ostensibly guaranteeing citizens equal protection under the law and outlawing race-based discrimination.

The Memphis Massacre, as the event came to be known, shows how lack of federal oversight and enforcement can make a mockery of even the most robust civil-rights laws. Former Confederates could murder, rob, and rape African Americans with impunity. Although much has changed since the end of the Civil War, the fact remains that political violence undermines the democratic process even where civil-rights protections are supposedly in place.

In many ways, Tennessee was a model of reunification. The state had a Republican majority assembly and governor. Ulysses S. Grant would carry Memphis’s Shelby County in two presidential elections aided by African American men, to whom the state extended voting rights in 1867, three years before the Fifteenth Amendment. During the Civil War, Memphis was a beacon to freed people. Union forces had captured it in June of 1862, and the city on the Mississippi River attracted thousands of formerly enslaved people. It was diverse, too: By 1866, Memphis was home to Yankees, Jews, and Germans. The city was roughly one-fifth Irish, including 90 percent of its police and 87 percent of its fire department.

But as in so many corners of the Confederacy, the camps where former slaves lived swelled with the hungry, the sick, and those seeking to find opportunity and family. The Memphis refugee or “contraband” camps bred suspicion and hatred among local whites. Black Memphians competed with the Irish for low-paying jobs. Following the war’s end—in Memphis as elsewhere in the former Confederacy—politicians prioritized peace with ex-Confederates over justice for African Americans.

This set the stage for the violent days of May 1866. When the rumor of the black-on-white crime spread, Fort Pickering’s commander, General George Stoneman, confiscated black soldiers’ weapons and ordered them to their barracks. That left a nearby black neighborhood and an African American refugee camp unguarded. The next evening, a brawl broke out on South Street between white police and newly discharged black veterans of the 3rd U.S. Colored Heavy Artillery. Around the same time, a white mob assembled, including police and firemen, and attacked the camp of former slaves and African American neighborhoods.

Government officials led the mob. City Recorder John C. Creighton rallied the attackers, saying, “Boys, I want you to go ahead and kill every damned one of the nigger race and burn up the cradle.” Defying the orders of the Shelby County sheriff, the rioters fanned out from Causey and Vance Streets. That night, “the Negroes were hunted down by police, firemen and other white citizens, shot, assaulted, robbed, and in many instances their houses searched under the pretense of hunting for concealed arms, plundered, and then set on fire,” according to an Army investigation. “During [this] no resistance . . . was offered by the Negroes.”

Violence resumed late the next morning when “a posse of police and citizens again appeared in South Memphis and commenced an indiscriminate attack upon the Negroes, they were shot down without mercy, women suffered alike with the men, and in several instances little children were killed by these miscreants.” For the next two days, the city seemed to be at the mercy of the mob. “All crimes imaginable were committed from simple larceny to rape and murder,” the Army investigator reported. “Several women and children were shot in bed.” An African American woman, Rachel Johnson, “was shot and then thrown into the flames of a burning house and consumed. Another was forced twice through the flames and finally escaped. In some instances houses were [set ablaze] and armed men guarded them to prevent the escape of those inside.”

In the aftermath, no arrests or attempts at prosecution were made. Federal civil-rights enforcement was lacking, and General Stoneman refused to intervene. Memphis Mayor John Park washed his hands of the matter. Congress investigated, producing a detailed report. But there were no arrests, no trials, and no convictions. Even if the Fourteenth Amendment seemed to solve the legal problems of Reconstruction, there was no political will to bring the perpetrators to justice.

The Massacre showed the failures of Reconstruction even as congressional Republicans seized control from President Andrew Johnson, a Tennessean and former military governor of the state. Johnson’s lenient national policies toward rank-and-file ex-Confederates promoted peace and a speedy political reunification after the war ended in 1865. Ex-Confederate states reentered the Union on ex-Confederate terms.

White supremacy prevailed. The earliest version of the Ku Klux Klan formed in December 1865. Many Memphis businessmen who had supported the Confederacy were disenfranchised, and they refused to view civil authorities as legitimate. Tennessee outlawed integrated schools. Other states passed Black Codes restricting movement and undermining African Americans’ political activities. Mississippi passed a strict vagrancy statute aimed at forcing former slaves to work for former masters and forbade employers from luring workers with high wages. Newly elected legislators in states like South Carolina showed up in their old Rebel uniforms. And though white civil-rights supporters lived in Memphis and other cities, they were targets of violence—including during the Memphis Massacre.

Eventually, Congress wrested control of Reconstruction, passing the Civil Rights Act of 1866 and reauthorizing the Freedmen’s Bureau—which oversaw contracts and resettlement for former enslaved people and displaced whites—over Johnson’s vetoes. Legislators sent the Fourteenth Amendment to states for ratification, all while the president urged states not to approve the measure. After all, there was political benefit in this kind of aggressive legislating: African Americans made up the largest bloc of Union-loyal Southerners during the war and were potential Republican voters.

Looking back in 1868, a Harper’s Weekly writer shrewdly summed up Reconstruction’s failures. Confederates lost the war, he wrote, but the project of peace foundered. “[D]efeat never converts. It is to the defeated what persecution is to the persecuted. The cause becomes even more precious, and fidelity to it a more sacred duty. The history of the Southern States since the surrender shows this plainly.” The Johnson administration’s overture to ex-Confederates proved more tenacious than any civil-rights protections that followed. “The Black codes ... the denunciation and hatred of Union soldiers and loyal citizens; the massacres at Memphis and New Orleans; the refusals of the [Fourteenth] amendment; the terrorism at elections, were signs of the old vigor.”

In response to widespread political violence, Uncle Sam put teeth in federal civil-rights measures. The Enforcement Act of 1870 outlawed both state and private violence against African Americans, reenacting the 1866 Civil Rights Act under the auspices of the Fourteenth Amendment. The 1871 Ku Klux Klan Act further penalized private and organizational violence under authority of the Fifteenth Amendment.

But the Grant administration’s enforcement was uneven. In 1871, the federal government placed nine South Carolina counties under martial law, and federal courts convicted more than 100 defendants charged under these acts. In 1872 and 1873, courts made close to 900 total convictions in the South. But dismissals outnumbered convictions in 1873. Economic hard times set in, and nearly 90 percent of cases brought under the acts in 1874 were dismissed. By 1876 the number of convictions had plummeted to nearly zero. Even those convicted usually got light sentences.

By 1876 Reconstruction was in full retreat and, with it, federal civil-rights protections. The U.S. Supreme Court held in U.S. v. Cruikshank that the perpetrators of the 1873 Colfax Massacre in Louisiana could not be convicted for federal civil-rights violations because the Fourteenth Amendment’s equal-protection clause did not extend to individuals’ crimes, just state actions. The justices simply ignored the fact that perpetrators of the Colfax Massacre targeted politically active African Americans. In 1883, the Supreme Court overturned the Civil Rights Act of 1875 on similar grounds.

It took 90 years for the state-built edifice of Jim Crow to be torn down by the Civil Rights Acts of 1957, 1960, and 1964, along with the Voting Rights Act of 1965 and other legislation. Those civil-rights measures came in the wake of widespread civil unrest, including riots, bombings, and political murders. Martin Luther King Jr. was assassinated just blocks from the site of the Memphis Massacre in 1968.

A new retreat from Civil Rights is getting renewed momentum today in the wake of the 2013 decision Shelby County v. Holder. The U.S. Supreme Court’s conservative majority invalidated sections 4 and 5 of the Voting Rights Act. Section 4 established a formula to identify disenfranchisement and section 5 required federal review of proposed state changes to voting laws. The justices held that “Section 4’s formula is unconstitutional in light of current conditions.” By 2009, voter suppression had become “eradicated practices,” the court held.

But evidence suggests this isn’t the case. Before the ink was dry on Shelby County, Republican North Carolina legislators proposed H.B. 589. This required voters to present a driver’s license or state-identification card at the polls, which imposes a substantial cost and burden on would-be voters. A 2013 study by the North Carolina Board of Elections found that the law would disenfranchise 318,643 out of 6.4 million eligible North Carolina voters, including a disproportionate number of African Americans, 85 percent of whom were registered Democrats. A Buncombe County election official offered support for the measure in an interview, saying, “If it hurts a bunch of lazy blacks that want the government to give them everything, so be it.”

That sentiment, quickly retracted, is by no means the equivalent of the spark that lit the Memphis Massacre. But it echoes a trend toward political exclusion that historically worked in concert with violence against the disenfranchised. Today over half the states of the former Confederacy require voter identification at the polls, which disproportionately affects African Americans and low-income voters.

The Memphis Massacre shows that deadly violence and denials of citizens’ rights can happen even when civil-rights laws are in place, particularly when those laws are defanged or unenforced. And the ghosts of Memphis haunt the current campaign cycle. At a Donald Trump campaign event in Alabama in November of 2015, several white supporters punched and kicked a Black Lives Matter protester, Mercutio Southall, while yelling racial slurs at him. Trump responded by saying, “Maybe he should have been roughed up because it was absolutely disgusting what he was doing.” In Kentucky in March, Shiya Nwanguma, an African American college student, was mobbed at a Trump rally. “I was called a nigger and a cunt, and got kicked out,” she reported. At a North Carolina rally a week later, Rakeem Jones was punched by a white Trump supporter, after which security officers forced Jones to the floor and pinned his arms behind his back before ejecting him. After being charged with the assault, John McGraw defended it, telling an interviewer, “Yes he deserved it. The next time we see him, we might have to kill him.”