Final answer:
The siege at Yorktown began on September 28, 1781, leading to the British surrender on October 19, 1781, which marked the last major battle of the American Revolution.
Step-by-step explanation:
The siege at Yorktown began on September 28, 1781, when the American and French armies combined at Williamsburg, Virginia, and then marched down the peninsula to Yorktown. Lord Cornwallis's army was effectively trapped, with no possibility of moving westward. A turning point in this conflict was the defeat of the British fleet by the French, securing the bay and blocking the York River.
The siege came to an end with Cornwallis's army surrendering on October 19, 1781, after Cornwallis's attempted breakout on October 16 failed. This event was the last major action in the American Revolution and precipitated the end of the war, with tradition noting that the British band played "The World Turned Upside Down" during the surrender.
It's of note that among those fighting at Yorktown was Boyrereau Brinch, a Black Continental soldier depicted in Jean-Baptiste-Antoine de Verger's watercolor from 1781, which serves as a historical documentation of the pivotal siege.