North Colorado: 51st state

Like everything else -- by charter (and religion).

Pulled out "How the States Got Their Shapes" book:

England stipulated the borders of Delaware in an 1682 deed from King Charles II to his brother, the future King James II. Charles defined Delaware's northern border as a 12-mile radius surrounding the Dutch settlement at New Castle. The rest of Delaware, he stated, comprised the land south of that circle as far as Cape Henlopen.

Maryland lodged a protest. In response, the King's Board of Trade and Foreign Plantations ruled in 1685 that the charter creating Maryland was intended to include only land uninhabited by Christians at the time the charter was issued. The board then south to clarify the border, but the boundaries turned out to be anything but clear.

From the ruling: The tract of land lying between the River and Bay of Delaware and the Eastern Sea on the one side and Chesapeake Bay on the other, be divided into two equal parts by a line from the latitude of Cape Henlopen to the 40th degree of northern latitude.

But then it was discovered the point where the Delaware River crosses 40 degrees north is the Philadelphia docks. Then it was discovered that a line bisecting the land between the east coast and the Chesapeake from the latitude of Cape Henlopen to the 40th slices through the 12-mile radius around New Castle.

Delaware's western border was adjusted to be tangent to its 12-mile radius. But this line resulted in a sizable wedge among the neighboring borders and this pocket of uncertain jurisdiction invited all sorts of individuals engaged in behaviors that jurisdictions tend to "jurisdict."

To eliminate this problem, the cneter point of the arc was relocated in 1750 from the steeple of the old Dutch church to the courthouse and the smaller "wedge" that resulted was given to Delaware. This adjustment accounts for the fact that Delaware's northwestern border appears as if it just missed the state's northern arc.