Not long before his death in 1968, Martin Luther King Jr. published a book called “Where Do We Go From Here: Chaos or Community?” It was around the same time that King planned the Poor People’s Campaign in Washington, D.C., and joined Memphis, Tenn., sanitation workers in their protests.

King, a proponent of nonviolence, felt he had to say something about the rioting that had become a summer routine in cities: “A riot at bottom is the language of the unheard,” the activist wrote in his book.

Yet King couldn’t have known how the unheard would cry out in the days after his death on April 4, 1968. Washington and other cities, including Baltimore and Chicago, were ripped apart from the inside. According to Clay Risen’s new book, “A Nation on Fire: America in the Wake of the King Assassination,” “39 people were dead, more than 2,600 were injured, and 21,000 had been arrested. The damages were estimated at $65 million — about $385 million today.”

Those statistics are just the beginning of the details that Risen explores in his book. Risen, a D.C. resident and the managing editor of Democracy Journal, became interested in the riots after hearing his parents’ stories from the time.

His mother worked in a brokerage house near Farragut Square. She and other suburbanites had come to the city to work that day, assuming riots would follow the usual pattern and hold off until nightfall, Risen said. But soon whispers began around the office, and by early afternoon, there was a sense that something was coming.

“Suddenly the phone rang for one of her co-workers, who was an African-American woman whose mother lived up in Shaw, and the mother was on the phone and gave her the message,” Risen recounted in an interview. “And her co-worker hung up and said … there’s rioting up the street, and they’re coming this way. We all need to get out of here.”

As his mother and her co-workers hit the street and headed outward, they joined a growing crowd of other office employees with the same idea. Risen said his mother eventually got onto a bus and clearly remembers looking back as the bus crossed the Francis Scott Key Bridge and seeing smoke rising across the city.

Risen’s father, meanwhile, was serving his military duty as an engineer at the ammunition plant in Joliet, Ill. After King’s death, the commanding officer ordered everyone into the barracks, gave them ammunition and told them to put on uniforms. They were preparing for a serious conflict in Chicago.

“It struck me immediately that their worst fears seem ridiculous today — the idea that there was going to be a race war or some sort of really cataclysmic event,” Risen said.

With that in mind, Risen spent much of his story putting the riots in context. This was the fourth summer that rioting in inner cities was common, and police departments and military experts had formed theories and strategies for dealing with it. President Lyndon Johnson, beaten down by the struggle in Vietnam and struggling to draw attention to his domestic agenda, had announced five days before King’s death that he would not run for a second term. King was shifting his focus from strictly racial problems to economic problems and accordingly was planning the Poor People’s Campaign in Washington for that summer. Other civil rights leaders and organizations were flirting with militant philosophies.

On the night of King’s death, Stokely Carmichael, a former leader of the Student Nonviolent Coordinating Committee who had become more unpredictable after spending some time abroad, tried to calm crowds on U Street. Yet the next day, in a memorial service at Howard University, he incited angry listeners, according to Risen’s book.

“He told them, ‘Do not be out on the streets for looting tonight. We mean business. If you don’t come out tonight with your gun, stay at home.’ He pulled a pistol from his waistband and waved it in the air. Murmuring ran through the crowd. ‘Do you have your gun?’ ‘I have mine.’ ‘I wish I had a gun.’”

That day’s unrest is the same that drove Risen’s mother out of the city and led to National Guard troops occupying the nation’s capital. Hints of the destruction of that week are still in evidence in what were then the District’s thriving black corridors along U Street and H Street. Risen concludes his book with a look at the U Street neighborhood not far from his office today.

“Newcomers to the once predominantly black neighborhood are as likely to be white, Asian, or Hispanic; they are likely to be wealthy, or at least young and headed toward great wealth,” he writes. “And unless they stumble across an inconspicuous historic marker at U and Fourteenth, chances are they don’t even know the riots happened. Virtually every physical trace has been obliterated.”

Released in the year of the first black president and the 100th anniversary of the National Association for the Advancement of Colored People, this book reminds modern readers how far we have come and how far we have yet to go.