The Annual Lantern Ceremony takes place each year on the eve of Patriots’ Day, a public holiday in Massachusetts and Maine on the third Monday in April. The ceremony is held at the Old North Church in Boston, where, on April 18, 1775, the church sexton displayed two lanterns from the steeple, signaling Paul Revere‘s message that the British would come to Lexington and Concord across the Charles River. The Annual Lantern Ceremony commemorates the lighting of the two lamps. The centerpiece of the ceremony each year is a keynote address by a notable leader of the Boston area or beyond.
Source: The Free Dictionary