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The First Printed Map Settling the Boundary Dispute Between Maryland and Pennsylvania 

Fine example of the Penn-Lord Baltimore Treaty Map, the map engraved by John Senex to accompany the agreement between the two factions which established the boundary between Pennsylvania and Maryland and led to the creation of Delaware.

The present map is of exceptional importance, being the map prepared by the two parties to illustrate the agreement between the Proprietors of the Maryland and Pennsylvania Colonies as to where to locate the border between the two colonies and, indirectly, establishing the boundary for what would become the State of Delaware.

Prepared privately as a means of illustrating the agreement, it was not offered for sale at the time and would have only been available to the parties to the agreement, their lawyers and a few aids and Colonial officials. 

While intended as a final settlement of the dispute, an error in the location of Cape Hinlopen on this map would lead to another 30 years of fighting, before the boundary was finally resolved and the Mason Dixon Line surveyed in the 1760s.

Historical Overview

The story of the Penn-Baltimore Agreement has been told in great detail by Nicholas Wainwright in his article, Tale of a Runaway Cape: The Penn-Baltimore Agreement of 1732.

From the time of Penn's original grant of Pennsylvania in 1682, there was a dispute with the neighboring Maryland Colony over the boundary lines between the colonies.  Attempts to settle were futile for nearly 50 years. In 1731, the parties finally reached an initial settlement, offering maps of their own as guides, and as Wainwright says, "The map was really the key to the Agreement."  Lord Baltimore demanded use of his map, and the Penns agreed. 

Baltimore's map was delivered to the London mapmaker John Senex, where a printed example could be engraved. One proof strike of it, with a scale of miles, survives in the Penn Papers at the Historical Society of Pennsylvania. The scale was later erased and the map printed on each of the six final copies of the agreement. On May 10, 1732, Baltimore and the Penns signed off on the copies of the agreement.

The settlement was not well received in America and Lord Baltimore soon discovered that his map was inaccurate.  The map had mislocated Cape Henelopen on the Delaware coast, thereby giving the Penns more land than Lord Baltimore had thought.  Lord Baltimore petitioned the Chancery Court in London, seeking to set aside the agreement. The Chancery Court case resulted in several written briefs, with the Senex Map submitted as an exhibit to the court by the Penns.   Finally, in 1750 the Penns won the case and a final survey of the land was ordered. Several attempts to retain American surveyors resulted in further delays, apparently due to the lack of skill exhibited by the surveyors selected.  In 1763, Mason and Dixon were retained for the survey and the survey ultimately completed in 1769.

The Penn-Lord Baltimore Map

This is a second state of the original 1732 Senex plate (engraved by him and meant to accompany the six manuscript copies of the May 10, 1732 Articles of Agreement.  This second state was printed to accompany a pamphlet entitled TRUE COPIES OF I. THE AGREEMENT BETWEEN LORD BALTIMORE AND MESSIEURS PENN . . . , published in London in 1734, the first printed document addressing Baltimore's unwillingness to comply with the terms of the 1732 Agreement. The maps that came with the 1734 work have a double-ruled border, which was not present on the six copies printed in 1732 on parchment. Streeter noted that the TRUE COPIES were printed  "perhaps as a memorandum for use in petitions made to George II that year by Lord Baltimore and Richard Penn." The map was sometimes laid in, accounting for the current independence of this map without any visible signs of having been bound in, and explaining how copies of TRUE COPIES... are found without the map as often as with it. 

The map would later appear in the "Breviat," typically annotated in red to highlight for the Chancery Court the areas in dispute.

Provenance:  The present example was acquired from Brunk Auctions in December 2017, and was previously in the Colonial Williamsburg Collection.


The Senex map is very rare on the market.  This is the second example we have offered in over 25 years.  Only 3 of the original 6 copies of the 1732 printing survive, the other 3 having been destroyed by fire (the Lord Baltimore copies).  

Condition Description
Minor loss of neatline at top right.
John Senex Biography

John Senex (1678-1740) was one of the foremost mapmakers in England in the early eighteenth century. He was also a surveyor, globemaker, and geographer. As a young man, he was apprenticed to Robert Clavell, a bookseller. He worked with several mapmakers over the course of his career, including Jeremiah Seller and Charles Price. In 1728, Senex was elected as a Fellow of the Royal Society, a rarity for mapmakers. The Fellowship reflects his career-long association as engraver to the Society and publisher of maps by Edmund Halley, among other luminaries. He is best known for his English Atlas (1714), which remained in print until the 1760s. After his death in 1740 his widow, Mary, carried on the business until 1755. Thereafter, his stock was acquired by William Herbert and Robert Sayer (maps) and James Ferguson (globes).