Final answer:
Martin Luther King Jr. played a crucial role in the Montgomery Bus Boycott, led the March on Washington where he gave his 'I Have a Dream' speech, and championed nonviolent protest strategies, significantly advancing the Civil Rights Movement.
Step-by-step explanation:
Three Major Accomplishments of Martin Luther King Jr.
Dr. Martin Luther King Jr.'s leadership and advocacy were central to significant advances during the Civil Rights Movement. One major accomplishment was his role in the successful Montgomery Bus Boycott, which led to a Supreme Court ruling that segregated buses were unconstitutional. Another was his leadership in the March on Washington, where he delivered his iconic "I Have a Dream" speech and helped to set the stage for the Civil Rights Act of 1964 and the Voting Rights Act of 1965. Finally, his promotion of nonviolent protest strategies was instrumental in enacting change and remains a cornerstone of civil rights activism.