The Wedge (or Delaware Wedge) is a small tract of land along the borders of Delaware, Maryland and Pennsylvania. Ownership of the land was disputed until 1921; it is now recognized as part of Delaware. The tract was created primarily by the shortcomings of contemporary surveying techniques. It is bounded on the north by an eastern extension of the east-west portion of the Mason–Dixon Line, on the west by the north-south portion of the Mason–Dixon line, and on the southeast by the New Castle, Delaware Twelve-Mile Circle. The crossroads community of Mechanicsville, Delaware, lies within the area today.

en.wikipedia.org/wiki/The_Wedge_(border)