How did Slavery affect the American Revolution?

Hi, I have a essay due tommorow (rough draft section) and I'm stumped on slavery in the Revolution. My topic is discuss the either (only one) econmical, political, social, or any other -al factor of slavery that related to the Revolution. The Only one I've found is slaves fought with the Americans against the British, in hopes of freedom (even though some were free, and the Brit's were "giving" unlimited freedom if the slaves fought with them); But the MAIN thing is, this is pre and during Revolution---not post. So not the founding of the civil war, just how did slavery affect the Revolution? TIA :D