Final answer:
The exact year of the introduction of bucket brigades in the American colonies is not specified, but they likely came into use around or before the early to mid-1770s amidst the escalating conflicts leading to the American Revolution.
Step-by-step explanation:
While the exact year when the bucket brigade was first used in the American colonies cannot be ascertained from the provided information, it is vital to understand the context of the era to infer its likely period of introduction.
The references to the tensions and events leading to the American Revolution, such as the arrival of British troops in Boston, the stockpiling of weapons and gunpowder in Concord, the Boston Tea Party, and other acts of defiance against British rule, all indicate a period in which communal efforts like bucket brigades would have been important for protecting towns from fires, which could be both accidental and a result of military action.
If the bucket brigade were related to colonial military actions or the subsequent Revolutionary War, it could reasonably be speculated that it was in use by the time such conflicts began in earnest, likely at around or before the early to mid-1770s.