The Battles of Lexington and Concord, fought on April 19, 1775, kicked off the American Revolutionary War. Tensions had been building for years between residents of the colonies and the British authorities, particularly in Massachusetts. These were just the first military engagements of the American Revolutionary War which would last from 1775-1783.
Sons of Liberty - Well, those in Boston anyway. There were similar organizations scattered throughout the Thirteen Colonies in the years leading up to the American Revolutionary War, and, yes, "Sons of Liberty" was a common name ;