Del. Code tit. 29 § 201
The limits of the State are as follows: On the south, the divisional line between Delaware and Maryland; on the west, the divisional line between Delaware and Maryland extended northerly to its intersection with the southerly boundary line of Pennsylvania; on the north, the boundary line between Maryland and Pennsylvania extended easterly to its intersection with the 12 mile circle described from New Castle and the 12 mile circle extended to low water mark on the eastern side of the Delaware River; and on the east, the low water mark on the eastern side of the Delaware River within the 12 mile circle, the southerly perimeter of the 12 mile circle from its intersection with the low water mark westerly to the middle line of the Delaware River, the middle lines of the Delaware River and Bay below the 12 mile circle to the mouth of the Bay and the Atlantic Ocean.
29 Del. C. § 201