The Revolution's ideals of liberty and equality existed side by side with the brutal realities of human slavery. By the time of the Revolution, slavery existed in all the colonies, slaves made up 20 percent of the population, and their labor had become a vital contribution to the physical and economic development of the colonies. The existence of slavery created tensions that would strain the integrity of the United States for many decades to come.

The Society of Friends, a religious group also known as the Quakers, formed the first formal antislavery society in 1775. Throughout the Revolution, as the states struggled to find common ground, the issue of slavery was so divisive that it threatened to shatter their fragile union. Some prominent leaders of the Revolution raised their voices to oppose slavery on moral grounds. Slaves and free Africans embraced the principles of liberty and equality embedded in the Declaration as their own best hope for freedom and better treatment. Many, fighting as soldiers in the American armies, helped to defeat the British, while earning their freedom and gaining the respect and gratitude of some whites. And clinging to their own understanding of "all men are created equal," they pushed the country closer to living out the full promise of its words.