Dr. King served as a clergyman and community organizer who helped seat the Civil Rights Movement (of the 1950's and 1960's) in the Black Christian church, develop non-violent protest strategies, and pool a nation of supporters through faith. His far-reaching sermons and speeches arguably impacted many to change social perspectives racial equality through a peaceful, unified front. Although his method was not popular with activists who touted a preference to gain justice "by any means necessary" (see Malcolm X or Robert Williams, as examples), Dr. King's was a method that many could support. Opponents' responses were extreme; an increase in the killings of Black men, women, and children and their White allies accompanied each push during the Civil Rights Movement. (Over 1,400 demonstrations were recorded in 1963 alone.) Yet, Dr. King aimed to continue changing Blacks' moods from submission to activism -- to advance the quest for equity in schools, neighborhoods, jobs, and social spaces.
To suggest that Martin Luther King, Jr. was the primary catalyst for Blacks' civil rights would be irresponsible and short-sighted. Such a statement would negate hundreds of Black and White activists that preceded Dr. King's efforts to extend equal rights and recognition to United States citizens. Freedom movements for African slaves in the Americas began during the Transatlantic slave trade, and the battle against racism (via institutionalized policies) continues at present. Faith-based groups, organizations (e.g., the National Association for the Advancement of Colored People - NAACP), community schools (e.g., the Highlander Center), and individuals were already active in addressing the imbalance of rights. Dr. King was a more visible member of an ongoing movement against socially sanctioned racism. His impact: increasing attention to a long battle for justice through non-violent, faith-based means.
A reference: Zinn, Howard. (1999) A People's History of the United States. New York, NY: Perennial Classics.