Following the assassination of Martin Luther King Jr., a leading African-American civil rights activist, on April 4, 1968, Washington, D.C., experienced a four-day period of violent civil unrest and rioting. Part of the broader riots that affected at least 110 U.S. cities, those in Washington, D.C.—along with those in Chicago and in Baltimore—were among those with the greatest numbers of participants. President Lyndon B. Johnson called in the National Guard to the city on April 5, 1968, to assist the police department in quelling the unrest. Ultimately, 13 people were killed, with approximately 1,000 people injured and over 6,100 arrested.
Background.
Starting in the late 19th century through the 1960s, the ready availability of jobs in the United States government attracted many people to Washington, D.C., including African American men, women, and children. This era is known as the Great Migration. As a result, middle-class African American neighborhoods prospered, but the lower class was plagued by poor living conditions and fell deeper into poverty.
Despite the end of legally mandated racial segregation after the 1954 decision of "Brown v. Board of Education", the neighborhoods of Shaw, the Atlas District Northeast corridor, and Columbia Heights remained the centers of African-American commercial life in the city.
Pre-existing conditions.
Housing.
Housing in D.C. was deeply segregated. Most of the slums in the city were in the southern quarter of the city, and most of the inhabitants of these slums were black. The United States Commission on Civil Rights said in a 1962 report that housing was much harder to attain for blacks than for whites, and that the housing blacks could find within the city's border was in a severely worse condition than the housing of their white counterparts. The Commission also stated that it was the United States Department of Housing and Urban Development's (HUD) segregationist zoning plot for the city that was to blame for housing inequality. HUD also came under fire from a group called ACCESS (Action Coordinating Committee to End Segregation in Suburbs) when they protested HUD for giving federal money to buildings that restricted blacks from living in them.
Education.
Ghettoization resulting from housing discrimination led into a feedback loop of low property taxes and low funding for public schools in D.C., with many white parents sending children to private schools. Two-thirds of D.C.'s population was black, while 92% of public school children were black. Striking statistics such as one out of three ninth grade public school students ending up graduating gave way to rising frustration from the black majority towards the white-dominated government and only gave way to louder and louder calls for their demands to be met. The federal government granted $5.5 million under Title 1 of the Elementary and Secondary Education Act, however there were still many schools serving a majority of students in poverty that did not receive additional Title I funds.
Police.
With 80% of the D.C. police force being white and 67% of the city being black, tension between police and the community rose along with tension between whites and blacks before 1968. Harsh police tactics, which started in the South in the 1960s to put a buffer on civil rights protests, left inner-city nationwide blacks more scared of police than ever. In the years leading up to 1968, there were many incidents in which D.C.'s black community held protests and turned angry against white police officers. In 1965, the same time and place as Dr. Martin Luther King Jr. worked with white lawmakers to pass the Voting Rights Act of 1965, two white D.C. police officers arrested a group of black boys with ages ranging from 12 to 16 for playing basketball in an alley. This prompted majority black crowds to gather around police stations around the city throwing rocks and, in some cases, firecrackers. These small, disorderly protests would happen multiple times before the end of 1965. 
There were three programs put in place after a long string of controversial arrests of black people by white police officers:
In 1968, before the riots began, a popular black D.C. reverend said that relations between black residents and white cops had reached a "danger point."
Unemployment.
In June 1967, the national unemployment rate was 4% for white Americans and 8.4% for non-white Americans. In D.C., non-white unemployment was over 30% for much of the 1960s, many times higher than national rates.
Course of events.
Looting and arson.
On the evening of Thursday, April 4, as word of King's assassination in Memphis, Tennessee spread, crowds began to gather at the intersection of 14th and U Streets. Stokely Carmichael, the militant civil and political rights activist who had parted with King in 1966 and had been removed as head of the Student Nonviolent Coordinating Committee in 1967, led members of the SNCC to stores in the neighborhood demanding that they close out of respect. Although polite at first, the crowd fell out of control and began breaking windows. Carmichael, who supported the riots, told rioters to "go home and get your guns."
The disturbances began when a window was broken at the People's Drug Store at the intersection of 14th and U Streets, NW. An hour and half later, by 11 pm, window-smashing and looting spread throughout the area. Looting occurred generally where there was little police protection. The local police department could not handle the disturbance, as one officer said, "This situation is out of control, we need help it's too much for us to handle." The civil disturbance unit was later activated, but by the time order was restored around 3 am, 200 stores had their windows broken and 150 stores were looted, most of them emptied. Black store owners wrote "Soul Brother" on their storefronts so that rioters would spare their stores.
The looting and arson spread throughout DC by April 5 with 4 major areas containing much of the violence, the first being the downtown area where many department stores were looted which was bounded by H Street NW in the north, F Street NW in the south, 15th Street NW in the west, and 7th Street NW in the east. The second area hit was along 7th Street NW from K to P Streets, which was where much of the fires took place and drained much police manpower. The third area hit was an over 2-mile long strip along 14th Street from downtown F Street NW to Park Rd, halfway to the border with Maryland. Another area of looting and arson was the area across the Anacostia River in Southeast DC, where 2 deaths took place. 
The District of Columbia Fire and Emergency Medical Services Department reported 1,180 fires between March 30 and April 14, 1968, as arsonists set buildings ablaze.
Carmichael speeches.
The next morning, Mayor-Commissioner Walter Washington ordered the damage cleaned up immediately. However, at 10 am, anger and discontent was still evident, and was exacerbated when Carmichael addressed a rally, saying "white America has declared war on black America", there is "no alternative to retribution" and "Black people have to survive, and the only way they will survive is by getting guns". "White America killed Dr. King last night. She made a whole lot easier for a whole lot of black people today. There no longer needs to be intellectual discussions, black people know that they have to get guns. White America will live to cry that she killed Dr. King last night. It would have been better if she had killed Rap Brown and/or Stokely Carmichael, but when she killed Dr. King, she lost." "I think white America made its biggest mistake when they killed Dr. King last night... He was the one man in our race who was trying to preach mercy and forgiveness for what the white man has done." He said "Execution of this retaliation will not be in the courts but in the streets...We're going to die on our feet-we're tired of living on our stomachs."
During a Havana broadcast, he told blacks to stay away from their jobs to protest the slaying and "make the white racist Americans understand that Negroes have the necessary force to set right the outrages which have been made against Negroes in the United States."
Clashes with police and firefighters.
Rioters walking down 7th Street NW and in the Atlas District came into violent confrontations with police. Around midday, arsonists set buildings ablaze while firefighters were attacked with bottles and rocks and unable to address the fires. By 1 pm, the riot was once again in full effect. Police unsuccessfully attempted to control the crowds using tear gas.
Presidential radio address.
In a radio address after the announcement of King's death, President Lyndon B. Johnson asked all citizens not to resort to violence. The following morning, he held a meeting at the White House with black civil rights leaders and government officials. He made a statement saying to "deny violence its victory," pleading that all citizens come together to keep King's dream alive. He declared the Sunday of that week to be Martin Luther King Jr. Day, a day of mourning, and ordered that all American flags be flown at half staff. He also made the final decision to bring in the military to stop the rioting.
Mayor-Commissioner Walter E. Washington attempts to quell the violence.
Walter Washington made nightly appearances during the riots, and these appearances were credited by many in the city with helping dampen the violence during the time. In addition, he refused FBI director J. Edgar Hoover's commands to shoot at rioters on the grounds that it would be needless slaughter and to avoid nearby harm to civilians. In 1974, Washington became the city's first elected mayor and its first black mayor, but only served one term after being overwhelmed with managing the city.
Coordination by Cyrus Vance.
Cyrus Vance was the former Deputy Secretary of Defense and special Pentagon representative in D.C. 1968 Riots. Mayor Washington acted with Vance's guidance during Thursday night, the first hours of rioting. He also acted as the Pentagon's special representative from Friday night and on. He was called upon by Mayor Washington on Friday afternoon to coordinate the National Guard, the Army, and the police. He was the leading force in a shift in the military emphasis which focused on the overwhelming use of men, the use of tear gas, and an early, strictly enforced curfew.
Police response.
Before the riots, John Layton, the police chief of Washington, emphasized that if there ever was a riot in Washington, he would use a large number of policemen with no guns, rather than fewer policemen with guns. During the riots, Layton put those words into action. Rather than acting immediately to the reports of rioting, looting, and window-breakings with a smaller force, he played the waiting game until a large enough force could be brought together. They then used tear gas instead of bullets to disrupt the rioting.
Military intervention.
On Friday, April 5, President Johnson invoked the Insurrection Act of 1807 and dispatched 11,850 federal troops along with 1,750 D.C. Army National Guardsmen to assist the overwhelmed D.C. police force. Marines mounted machine guns on the steps of the Capitol and Army soldiers from the 3rd Infantry Regiment guarded the White House. The 2nd Brigade of the 82nd Airborne Division from Fort Bragg, North Carolina and 6th Cavalry Regiment from Fort Meade, Maryland were among the principal federal forces sent to the city. At one point, on April 5, rioting reached within two blocks of the White House before rioters retreated. The occupation of Washington was the largest of any American city since the Civil War.
Federal troops and National Guardsmen imposed a strict curfew, worked riot control, patrolled the streets, guarded looted stores, and provided aid to those who were displaced by the rioting. They continued to remain after the rioting had officially ceased to protect against a second riot and further damage.
Deaths.
By Sunday, April 7, when the city was considered pacified, 13 people had been killed in fires, by police officers, or by rioters. An additional 1,097 people were injured and over 7,600 people were arrested.
Civil Rights Act.
On April 11, 1968, Johnson signed the Civil Rights Act of 1968, which included the Fair Housing Act section that prohibited discrimination concerning the sale, rental, and financing of housing based on race, religion, national origin, or gender. While a bill had been in question for some time, Johnson sped up the process following the assassination of Dr. King. The Act helped desegregate D.C.