Check Out: Over 40 Speeches and Sermons by Martin Luther King, Jr. on Our LearnOutLoud MLK Audio & Video Page.
"When the architects of our republic wrote the magnificent words of the Constitution and the Declaration of Independence, they were signing a promissory note to which every American was to fall heir. This note was a promise that all men, yes, black men as well as white men, would be guaranteed the "unalienable Rights" of "Life, Liberty and the pursuit of Happiness." It is obvious today that America has defaulted on this promissory note, insofar as her citizens of color are concerned. Instead of honoring this sacred obligation, America has given the Negro people a bad check, a check which has come back marked "insufficient funds."
-Martin Luther King, Jr.
This speech was delivered on August 28, 1963, at the Lincoln Memorial, Washington D.C.