A small town in the state of Virginia, in the United States. It is famous for one thing: in 1781, during the American Revolutionary War (the war in which Americans won independence from Britain), the British army under Cornwallis was trapped there — American troops on land, French ships blocking the sea — and surrendered. That surrender is usually treated as the end of the fighting, though the formal peace treaty came two years later. So when Americans say "Yorktown", they usually mean the battle, not the town: "after Yorktown" means "after the war was effectively won". It is a place name, always capitalised. Several US ships have been named USS Yorktown after it, and you may meet the name that way too.