On November 4, 1956, King delivered a sermon to the congregation of the Dexter Avenue Baptist Church in Montgomery, Alabama in the form of a fictional letter from the apostle Paul to American Christians of the 1950s. As the church’s pastor, King used this unconventional format to draw attention to the widening gap between the country’s moral and spiritual progress, and its scientific and technological development. He also took on the potential dangers of capitalism, and the destructive evil of segregation. King delivered this sermon again at a meeting of the Commission on Ecumenical Mission and Relations in Pittsburgh on June 3, 1958.

“I am afraid that many among you are more concerned about making a living than making a life. You are prone to judge the success of your profession by the index of your salary and the size of the wheelbase on your automobile, rather than the quality of your service to humanity. The misuse of Capitalism can also lead to tragic exploitation.”

King gave his most famous speech on the steps of the Lincoln Memorial at the March on Washington for Jobs and Freedom on August 28, 1963 to a crowd of more than 250,000 people. He had been making direct references to the American dream in speeches since 1960, and, originally, this wasn’t going to be part of his speech that day in the nation’s capital.

“I started out reading the speech, and I read it down to a point … the audience response was wonderful that day … And all of a sudden this thing came to me that … I’d used many times before ... ‘I have a dream,’” King told Donald H. Smith in an interview on November 29, 1963. “And I just felt that I wanted to use it here … I used it, and at that point I just turned aside from the manuscript altogether. I didn’t come back to it.”

The primary message he conveyed through both his list of dreams and the original speech was one calling for racial justice by way of ending segregation and discrimination.

“We can never be satisfied as long as our children are stripped of their selfhood and robbed of their dignity by signs stating 'For Whites Only.' We cannot be satisfied as long as a Negro in Mississippi cannot vote and a Negro in New York believes he has nothing for which to vote. No, no, we are not satisfied and we will not be satisfied until justice rolls down like waters and righteousness like a mighty stream.”

On December 11, 1964, King delivered a lecture in the auditorium of the University of Oslo after officially being awarded the Nobel Peace Prize the day before. Speaking to an audience of Norwegian monarchs and politicians, as well as the Nobel Prize Committee, King's lecture was more academic than his usual speeches, while still touching on the same themes of racial justice, nonviolent resistance, and moral and spiritual development. He also made a case as to why economic inequality must be addressed and included in any path towards peace, referring to poverty as “one of the most urgent items on the agenda of modern life.”

"I am only too well aware of the human weaknesses and failures which exist, the doubts about the efficacy of nonviolence, and the open advocacy of violence by some. But I am still convinced that nonviolence is both the most practically sound and morally excellent way to grapple with the age-old problem of racial injustice."

Although King had spoken about his opposition to the Vietnam War publicly since 1965, his “Beyond Vietnam” speech—delivered on April 4, 1967—is considered his first major public statement that centered on making a case against American involvement in the conflict.

Addressing a crowd of approximately 3,000 people in Riverside Church in New York City, King outlined seven reasons why he thought it was time that he, as a civil rights leader and Nobel Peace Prize winner, needed to take a stance on the Vietnam War. These included the economic burdens of sending American troops to fight in Vietnam (which he said amounted to a “cruel manipulation of the poor”), and the ongoing violence against Vietnamese civilians caught in the crossfire. This ended up being one of King’s most controversial speeches.

“Perhaps a more tragic recognition of reality took place when it became clear to me that the war was doing far more than devastating the hopes of the poor at home. It was sending their sons and their brothers and their husbands to fight and to die in extraordinarily high proportions relative to the rest of the population. We were taking the Black young men who had been crippled by our society and sending them eight thousand miles away to guarantee liberties in Southeast Asia which they had not found in southwest Georgia and East Harlem.”

Only 10 days after making his case against the Vietnam War, King took the stage at Stanford University on April 14, 1967 and delivered another one of his most iconic speeches to an audience of university faculty and students. In an effort to draw attention to the widening poverty gap and systemic social and economic inequality in the United States, he described “two Americas”: one of prosperity and the other of poverty. King also stressed that “racism is still alive in American society,” in both the North and South, and how every time the country appears to be taking a step towards racial justice, it's followed by multiple backwards steps.

"Our nation's summers of riots are caused by our nation’s winters of delay. And as long as America postpones justice, we stand in the position of having these recurrences of violence and riots over and over again. Social justice and progress are the absolute guarantors of riot prevention.”

On August 31, 1967, King delivered the keynote address at the National Conference on New Politics in Chicago to an audience of roughly 3,000 people. In his speech, he made the case that racism, excessive materialism and militarism are all forms of violence that exist in a vicious cycle, referring to them as the “three evils” of American society. Lasting nearly 45 minutes, King’s address discusses the existence of racism since the birth of the country, and calls on the government to end the war in Vietnam, and enact policies to alleviate poverty.

“For the good of America, it is necessary to refute the idea that the dominant ideology in our country, even today, is freedom and equality while racism is just an occasional departure from the norm on the part of a few bigoted extremists. Racism can well be that corrosive evil that will bring down the curtain on western civilization.”

King gave his final speech on April 3, 1968 at Mason Temple in Memphis, fewer than 24 hours before he was assassinated. Striking sanitation workers packed the church beyond capacity to see King on his third trip to Memphis in support of their cause in less than a month. In his address, he explains that if given the choice to live during any period of human history, he would have chosen the second-half of the 20th century because grappling with racial, social and economic injustices were a matter of survival. From there, he called on those in attendance to remain united in their fight against injustice without the use of violence.

“We've got to give ourselves to this struggle until the end. Nothing would be more tragic than to stop at this point, in Memphis. We've got to see it through. And when we have our march, you need to be there. Be concerned about your brother. You may not be on strike, but either we go up together, or we go down together.”