Year after year, legions of school children read and commit to memory Martin Luther King's "I have a Dream" speech. Many of them believe it is his most important statement.

It's the speech he delivered during the March on Washington for Jobs and Freedom on August 28, 1963. King spoke in front of the Lincoln Memorial to about 250,000 people advocating racial harmony. King's speech is often recited on Martin Luther King Day, the government holiday used to reflect on his legacy.

A Call For Unity is a letter written on April 12, 1963 by eight white clergymen from Birmingham, Ala. They urged an end to the demonstrations by blacks "directed and led in part by outsiders." They urged blacks to negotiate and use the courts if rights were being denied.

Letter from Birmingham City Jail, is an open letter written on April 16, 1963 by civil right leader Martin Luther King Jr. King wrote the letter from the city jail in Birmingham, Ala., after a peaceful protest against segregation. His letter responds to a statement made by eight white Alabama clergymen on April 12, 1963 titled A Call For Unity.reets

King's original letter: