The Emmett Till trial in September 1955 was the early catalyst for the civil rights movement. McMahon's on-site and on-deadline images from Mississippi, published nationwide in "Life" magazine, provided the visualization that helped spur Rosa Parks' refusal to give up her seat on the bus in December 1955, which then led to the Montgomery bus boycott and to bringing Martin Luther King Jr. to national attention, along with fellow boycott leader Ralph Abernathy. McMahon was in attendance for King's "I Have a Dream" speech during the August 1963 March on Washington for Jobs and Freedom. He also covered the two 1964 mistrials of the murderer of civil rights leader Medgar Evers. In March 1965, King's march for black enfranchisement was going from Selma to the Alabama Capital Montgomery. About that time, Franklin was returning from Cape Kennedy, Florida, after covering one of the U. S.'s manned space launches. He heard of the march on his car radio, and took a detour, arriving in time to document King's arrival in Montgomery. He also covered King in Chicago in 1966, the United Farm Workers protest in 1968, and the 1968 Chicago riots following King's death.