Martin Luther King Jr. is known for his pivotal role in the civil rights movement in the United States. As a prominent leader, he advocated for nonviolent protest and civil disobedience to combat racial segregation and discrimination. King is best known for his ability to mobilize mass movements and deliver inspiring speeches, including his famous "I Have a Dream" speech during the 1963 March on Washington. His efforts were instrumental in the passage of the Civil Rights Act of 1964 and the Voting Rights Act of 1965, making significant advancements towards equality for African Americans.