Freedom Trail
Because the steeple was the tallest in Boston at the time, it played an important role just before the American Revolution started.  Just before the Battles of Lexington and Concord, the first battles of the Revolution, the British had two choices for how they could get to Lexington and Concord.  They could walk, or they could row across the Charles River.  The Sons of Liberty hung two lanterns in the church's steeple to signal that British soldiers were crossing the Charles River.  This helped the Americans figure out the best way to defend against the British.