The assassination of Dr. Martin Luther King had profound and lasting effects in the world of race relations and, indeed, in the United States at large. In the days following the assassination, cities across the nation erupted in violence and riots. Eventually, more than sixty cities nationwide would experience violent outbreaks due to the assassination.

The White House reaction to the assassination was equally significant, with President Lyndon B. Johnson declaring a national day of mourning on the day of Dr. King's funeral. Fearing the reaction his presence might bring to the funeral, President Johnson sent his Vice-President, Hubert Humphrey to Dr. King's funeral in his stead. Dr. King's funeral was attended by more than three hundred thousand people. Dr. King's widow, Coretta Scott-King, requested that Dr. King's eulogy consist of his last recorded sermon. Dr. King's specific requests for his funeral were that he not be remembered for awards, titles, or honors, but rather that he be remembered as a champion for the poor, the disenfranchised, the destitute, and humanity in general. One of Dr. King's close friends sang a favorite hymn of Dr. King's, "Take My Hand, Precious Lord".

A manhunt was launched for Dr. King's killer, and authorities arrested James Earl Ray two months after the assassination. Ray had been trying to fly out of Heathrow Airport, in the United Kingdom, with a falsified Canadian passport when he was captured. After being extradited to Tennessee, he confessed to the murder of Dr. King, a confession which he recanted after three days. He did, however, plead guilty to avoid the death penalty, and was subsequently sentenced to 99 years in prison. James Earl Ray staged a prison break, along with six other inmates of the federal penitentiary where he was incarcerated. He was returned to prison three days later, and tried, unsuccessfully to petition the courts for a retrial. Ray found a somewhat sympathetic ear in the son of the slain Dr. Martin Luther King, Dexter. Dexter King met with James Earl Ray in prison, in 1997, and was sufficiently convinced that Ray deserved a retrial. Despite this endorsement, James Earl Ray died in prison without ever having received a second trial.

There have been some, within the African-American civil rights community, who have suggested that the United Sates government may have had some involvement with the assassination of Dr. King. Jesse Jackson, who notably was with Dr. King when he was murdered, has said that he believes the government aided James Earl Ray, both in the execution of the assassination, and in his subsequent (albeit temporary) escape. He has also said he believes the government had infiltrated Dr. King's inner circle. Like many another alleged conspiracy, the truth in this case may never be known.