[5][6] The decision helped end the 85-year dispute over the Pennsylvania–Maryland border,[7] although the issue was not definitively resolved until King George III formally approved the newly surveyed Mason–Dixon boundaries in 1768.

[8] Conflicts between settlers such as Cresap's War and questions surrounding to which proprietor they owed taxes prompted both sides to desire a settlement.

On 10 May 1732, Calvert and the Penns signed an Article of Agreement which reaffirmed much of the 1685 ruling, but adjusted Pennsylvania's southern boundary below the 40th parallel.

[6] Lord Baltimore had also discovered the mapping error that resulted in Fenwick Island being used as the southernmost boundary point in the Articles of Agreement, rather than Cape Henlopen, and he protested this.

King George II issued a decree on 4 May 1738 barring either proprietor from making any land grants in the disputed territory, and creating temporary boundary lines.

In it the court declined to make any final order until the Attorney General was joined as a party, but noted the same concerns as the subsequent decision relating to land overseas.

[6] He commenced his judgment by noting the importance of the matter, calling as it did for "the determination of the right and boundaries of two great provincial governments and three counties; of a nature worthy the judicature of a Roman senate rather than of a single judge".

In relation to the delay point, he noted that time only ran from the default not the agreement, and in any event equity could grant relief in such cases.

In November of that year, the Commissioners met in New Castle, agreed to the Transpeninsular Survey results, and placed the Middle Point marker.

[5] In 1761, the colonial surveyors made an attempt at surveying the Twelve mile circle by laying a chain in a line from the Court House's cupola, but they were unsuccessful due their tools and bad calculations.

They then proceeded 31 miles west where they set up their headquarters for the project on the Harlan Farm in Embreeville and erected a stone as a reference point.

Ironically the decision giving rise to the exception (Penn v Baltimore) precedes the case establishing the general rule (British South Africa Co v Companhia de Moçambique [1893] AC 602) by nearly 150 years.

Indeed, in the Moçambique case, it expressly refers to Penn v Baltimore: Courts of Equity have from the time of Lord Hardwicke’s decision in Penn v Baltimore exercised jurisdiction in personam in relation to foreign land against persons locally within the jurisdiction of the English court in cases of contract, fraud and trust.

Cheshire & North refers to an even earlier case where broadly the same principle was applied in relation to land in Ireland: Archer v Preston, undated, but cited in Arglasse v Muschamp (1682) 1 Vern 75 at 77, 23 ER 322.

[4] Be that as it may, the case is now universally cited and relied upon for the board proposition that the court can enforce personal rights relating to land abroad by exercising jurisdiction over the parties.

Professor Adrian Briggs of Oxford University has asserted that the judicial precedent is sufficiently important that there should be a similar eponymous rule referring to the case itself.

[24] Cheshire North & Fawcett refers to the comments of Lord Esher MR in the Moçambique case that the decision in Penn v Baltimore, "seems to me to be open to the strong objection, that the Court is doing indirectly what it dare not do directly".

As one of the earliest attempts by the courts to adjudicate boundary disputes between colonies or states in America, Penn v Baltimore has been relied upon as precedent for numerous other cases involving American boundary disputes, particularly Lord Hardwicke's assertion that "long possession and enjoyment... is one of the best evidence of title to lands or districts of lands in America.

Reported decisions include: In the United States it was cited by the US Supreme Court on several occasions:[31] New York Attorney General Josiah Ogden Hoffman cited Penn v Baltimore in the case of New York v. Connecticut, 4 U.S. 1 (1799), which was the first case heard by the Supreme Court under its original jurisdiction authority to resolve disputes between states.