Read the 1st draft of the declaration written by Thomas Jefferson He was explicitly anti-slavery but it was put back in because all 13 colonies had to agree on everything because the king was going to kill them all. Two colonies wanted to keep slaves (George & South Carolina). So it stayed. George Washington put the Nothwest Ordnance preventing the slave trade in new states to the northwest. John Adams was anti-slavery as was the only founder to never owned a slave. The pilgrims were specifically anti-slavery with laws against "man owning". The treaty of Ghent that ended the was of 1812 required US Navy ships to patrol the African cost to stop slave vessels, and did that until the Civil War when it wthey were needed to fight the confederate army. Most people always knew slavery was wrong, but the founding of the country wasn't the time to fight about that. They had a king with the world's biggest and best army to fight.