The pivotal event in 1775 that served as the beginning of the American Revolutionary War was the Battles of Lexington and Concord. These skirmishes, occurring on April 19, 1775, were the first military engagements between British troops and colonial militia. The confrontations stemmed from colonial resistance to British taxation and laws, exemplifying rising tensions. The phrase “the shot heard round the world” describes the significance of these battles, symbolizing the start of a struggle for independence that would lead to the founding of the United States and influence revolutions globally.