In a speech delivered on the steps of the Lincoln Memorial during the 1963 March on Washington, Reverand Dr. Martin Luther King Jr. invoked the promises made in the Declaration of Independence, the U.S. Constitution, and the Gettysburg Address, calling on the nation to deliver on the promissory note of equal rights made but not yet paid to African Americans. An estimated 250,000 March participants, as well as a national television audience, heard the speech that has since passed into history as a defining moment of the Civil Rights movement.