Page "Delaware" Paragraph 9

This border extends all the way east to the low-tide mark on the New Jersey shore, then continues south along the shoreline until it again reaches the 12-mile ( 19 km ) arc in the south ; then the boundary continues in a more conventional way in the middle of the main channel ( thalweg ) of the Delaware River.

To the west, a portion of the arc extends past the easternmost edge of Maryland.

The remaining western border runs slightly east of due south from its intersection with the arc.

The Wedge of land between the northwest part of the arc and the Maryland border was claimed by both Delaware and Pennsylvania until 1921, when Delaware's claim was confirmed.