Simplify the following text for a Grade 6 native English-speaking person.
Original: Martin Luther King , Jr. ( January 15 , 1929 â `` April 4 , 1968 ) was an American clergyman , activist , and prominent leader in the African American civil rights movement .
Simplified: Dr. Martin Luther King , Junior ( January 15 , 1929 â `` April 4 , 1968 ) was a famous American . He fought for civil rights .