Martin Luther King Jr. was a Baptist minister and civil rights activist who was assassinated in 1968 at the age of 39. He is best known for his iconic "I Have a Dream" speech delivered in 1963 to 250,000 people attending the March on Washington, where he advocated for racial equality and an end to segregation. King played a pivotal role in the Civil Rights Movement through his advocacy for nonviolent protest and was awarded the Nobel Peace Prize in 1964.