The major event remembered as the "shot heard 'round the world" refers to the opening conflict of the American Revolutionary War at the Battles of Lexington and Concord on April 19, 1775. This phrase captures the idea that a single event in the American colonies sparked a larger revolution. British troops aimed to seize colonial military supplies, but colonial militia confronted them, leading to the first shots fired. This confrontation galvanized colonial resistance, marking a pivotal moment in the struggle for independence and ultimately igniting a battle for freedom that would lead to the creation of the United States.