Which event marked the beginning of the American Revolution?

The Battles of Lexington and Concord in 1775 are recognized as the beginning of the American Revolution because they represented the first military engagements between British troops and colonial militias. These battles were the culmination of rising tensions and conflicts between the colonies and Britain over various issues, including taxation without representation and British military presence. When the "shot heard 'round the world" was fired at Lexington, it signified the start of armed conflict and galvanized the colonies in their pursuit of independence.

The Boston Tea Party occurred in 1773 and was a significant protest against British taxation policies, but it did not involve armed conflict and therefore did not initiate the Revolutionary War. The Declaration of Independence, adopted in 1776, formally declared the colonies' separation from Britain, but it was a result of the ongoing war, not its inception. The signing of the Treaty of Paris in 1783 marked the conclusion of the war, cementing American independence, well after hostilities began. Thus, the Battles of Lexington and Concord directly represent the spark that ignited the American Revolution, making it the correct answer.