A prominent civil rights leader, Martin Luther King Jr. advocated for racial equality and justice for African Americans in the U.S. His philosophy of nonviolent resistance and powerful oratory, exemplified in his famous "I Have a Dream" speech, galvanized public support for the civil rights movement. King’s leadership in events like the Montgomery Bus Boycott and the March on Washington significantly advanced the fight against segregation and discrimination, earning him a lasting legacy in American history.