A duchy is a territory, fief, or domain ruled by a duke or duchess. Historically, some duchies in Continental Europe were sovereign, while others (especially in France and Britain) were subordinate districts of a kingdom.
Duchies in the United Kingdom
The only modern duchies in the United Kingdom are those of Cornwall and Lancaster. Unlike historic duchies, these are no longer associated with a distinct geographic area. Rather, they are "Crown bodies," regulated by Acts of Parliament, that have some of the powers of a corporation or trust. They invest primarily in land, and their income is payable either to the monarch or the monarch's eldest son.
The Duchy of Cornwall currently owns approximately 141,000 acres (57,000 hectares) in England. This includes just over 2% of the county of Cornwall. The majority of the estate lies elswhere, with half being on Dartmoor in Devon. The income of the Duchy of Cornwall accrues to the Duke of Cornwall, who is the monarch's eldest son if heir to the throne (and thus currently the Prince of Wales). The estate reported a profit of over £7,800,000 for the year ending March 31, 2002.