Martin Luther King Jr. played a pivotal role in the American civil rights movement as a leading advocate for nonviolent protest against racial segregation and injustice. He emerged as a prominent leader in the 1950s and 1960s, spearheading initiatives like the Montgomery Bus Boycott and the March on Washington, where he delivered his iconic "I Have a Dream" speech in 1963. King emphasized the principles of nonviolence and civil disobedience, inspired by Mahatma Gandhi’s philosophy. His leadership greatly advanced civil rights legislation, including the Civil Rights Act of 1964 and the Voting Rights Act of 1965, making lasting contributions to social justice.