Question

What marked the official beginning of the America revolution

Answer 1

it was on April 1775, that the battle of Lexington occurred, which was a then followed by the battle of Concord. The shot at Lexington marked the first blood spilled in the war of the American independence.
hope this helps ..

Answer 2

Battles of Lexington and Concord. First blood spill was referred to as the "Shot Heard Around The World" (in Lexington).