The first protest over the Stamp Act met under this tree in August of 1765. Shortly afterward, a plaque was nailed to the tree calling it the "Liberty Tree". Some say the name was meant to discourage violence from the crowds that met here, but that would be like naming a battlefield HappyGlade Smile-Farm and just crossing your fingers. Eventually, a flag pole was installed in the tree, and the flag flown to summon people to meetings.
Unpopular figures were hung in effigy from the tree's branches. The Sons of Liberty also used to issue "Summons" to the tree for supposed crimes (i.e. supporting unpopular British decrees, like the Stamp Act and Tea Act).
The idea caught on elsewhere - other towns designated their own liberty trees, or put up liberty poles. In New York there was an ongoing battle between the Sons of Liberty - who kept putting the poles up - and the British Authority - who kept taking them down, like an angry couple who can't decide whether the toilet seat should be up or down.
True to the British penchant for destroying anything the Rebels loved, soldiers and Loyalists chopped down this tree during the siege in 1775. It was used as firewood, which was in short supply. Modern Day Boston has a plaque over the tree's former location, but the tree itself has never been replaced. So much for environmental sustainability.