The Detroit Walk to Freedom
From Wikipedia: “The Walk to Freedom was a mass march during the Civil Rights Movement on June 23, 1963 in Detroit, Michigan. It drew crowds of an estimated 125,000 or more and was known as “the largest civil rights demonstration in the nation’s history” up to that date.” “It was a precursor to his famous “I Have a Dream” speech given weeks later in Washington, D.C.. The march itself was, to King and his supporters, partly a practice run of the March on Washington for Jobs and Freedom.” Whole Story on Wikipedia
Text of King’s Speech in Detroit
Recording of Speech on Youtube