For blacks, words promising liberty did not ring true Ours is the world's oldest written Constitution still in force, perhaps because it spelled out a process for change. For African Americans - treated as property in the original document - the evolution of rights spans two centuries.

The words were as fiery as the antislavery crusader William Lloyd Garrison could make them: The Constitution of the United States was nothing more than "a covenant with death and an agreement with hell."

That was in 1842, when the national argument over slavery was getting hotter and hotter.

A dozen years later, with the country even more bitterly divided over slavery and sliding toward the Civil War, Garrison burned a copy of the Constitution at a Fourth of July celebration in Framingham, Mass.

"So perish all compromises with tyranny," he declared.

That's a stinging indictment of a document whose stated aim is "to establish Justice, insure domestic Tranquility . . . and secure the Blessings of Liberty to ourselves and our Posterity."

But when it comes to race, the Constitution has not always met the ideals laid out so grandly in its preamble.

The Constitution, as it existed in Garrison's day, not only allowed slavery, but also gave the slave states disproportionate representation in Congress and in the Electoral College.

Not until after the Civil War, with the ratification of the 13th, 14th and 15th Amendments, did the nation enact a constitutional ban on slavery and extend the rights of citizenship to African Americans.

Even with those standards enshrined as part of the nation's fundamental law, the blessings of liberty have often proved elusive for African Americans.

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The framework of government that the delegates to the Constitutional Convention hammered together in Philadelphia in the summer of 1787 was not just a statement of political philosophy. It was a web of compromises, spun by men who were political doers as well as thinkers.

One of the most important compromises had to do with slavery. In return for Southern support of the Constitution, Northern delegates agreed to accept the existence of slavery and made important concessions to slaveowners.

The Constitution "not only strengthened slavery, but sanctioned it," said Roger Wilkins, professor of American culture at George Mason University in Fairfax, Va. "It gave [slavery] the trappings of national legitimacy."

After bitter debate, the convention agreed to count three-fifths of the slave population in computing the size of each state's congressional delegation - even though slaves were considered property and could not vote.

The three-fifths clause would remain the law of the land until the 14th Amendment was ratified in 1868.