Old North Church has been standing in Boston's North End since Christmas 1723, making it the city's oldest surviving church. Its steeple, blown down by hurricanes twice and rebuilt, has looked much the same for three centuries.

The church's claim on history rests on a single night. On 18 April 1775, sexton Robert Newman and fellow Patriot John Pulling climbed the belfry and hung two lanterns for sixty seconds. Two meant the British were advancing by sea. Newman had to repel down the building's rear to avoid six British officers renting its ground floor. Arrested the next day, he blithely convinced his captors he had no key, despite being the church's deacon and bell ringer.

VoiceMap's audio tours trace the full web behind that night's signal, placing the lanterns in the context of Boston's spy networks, Revere's escape across Charlestown Bay and the Revolutionary movement building in the streets below.