Benjamin Franklin played a crucial role in the American Revolution and continued serving in important government roles, advocating for abolition of slavery and rights of indigenous peoples. Martin Luther King Jr. led the Montgomery bus boycott and delivered his famous "I Have a Dream" speech, championing civil rights until his assassination in 1968. Nelson Mandela served 27 years in prison before becoming South Africa's first black president in 1994, advocating for issues like poverty and human rights.