In 1863 Abraham Lincoln signed the Emancipation Proclamation to free the slaves. He is the "great American" in whose "symbolic shadow" the attendees of King's address literally stand on the grounds before the Lincoln Monument in Washington DC, in August of 1963. However, Dr. King's reference is somewhat ironic, here, as he goes on to emphasize that precisely one hundred years later, black people remain, by any measure of equality, fundamentally not free, not free to vote, not free to peaceably assemble, not free from violence. While Lincoln's decree became "a beacon of hope" for African Americans, they exist still within the shadow of injustice and continued oppression. Further, assembled on the grounds of the nation's capital, it is manifestly apparent that the promises signified by this city designed (In part by black architect, Benjamin Banneker) as a series of monuments celebrating democracy, have not been delivered to black Americans. They have no political "capital" in this place, and they have come, in part, to reclaim and "cash the check" that came back marked "insufficient funds" on the promise of equality established by the Declaration of Independence and the Constitution.
