A Plan of the West Line or Parallel of Latitude which is the Boundary between the Provinces of Maryland and Pensylvania [sic], manuscript map surveyed, drawn, and signed by Charles Mason and Jeremiah Dixon, drawn in Philadelphia between December 26, 1767 and February 29, 1768, six sections on laid paper joined together, ink over graphite pencil with a double ruled ink border, signed “Cha. Mason/Jere: Dixon” at lower right in iron gall ink, sheet 6-1/2 x 76 in.; modern parcel gilt frame, 18 x 87-3/8 x 1-3/4 in.

Provenance: Benjamin Chew (1722-1810); Christie's, New York, NY, "Colonial American Documents including the Declaration of Independence from the Chew Family Papers", April 1, 1982, lot 23; Malcom S. Forbes for the Forbes Foundation; Christie's, New York, NY, "Forbes Collection of American Historical Documents", March 27, 2002, lot 4; Private Collection

Note: The original Mason-Dixon survey map, illustrating the boundary line between Maryland and Pennsylvania, resolved the longest running boundary dispute in American history, and is notably the most famous survey ever undertaken. In undertaking the first geodetic survey ever conducted, Mason and Dixon performed one of the greatest scientific achievements of its time. Measuring only 6-1/2 inches in height, this map represents one of the most symbolic icons of American history. More than half a century after Mason and Dixon surveyed the boundary, the line was extended westward as part of the Missouri Compromise, the law that effectively determined the division between free and slave states. Thus, more than just illustrating the resolution of a boundary dispute, the Mason-Dixon Line became an enduring symbol of the cultural and political divide between the North and the South. Furthering the symbolic significance of the Mason-Dixon Line, historians have suggested that the term "Dixie" referring to Southern culture, evolved from a linguistic shortening of Jeremiah Dixon’s name.

The origins of the dispute between William Penn and Cecil Calvert, Second Baron Baltimore

A variety of factors contributed to boundary line controversies in the American colonies — geographical errors, a general lack of understanding of the geography, and monarchs reissuing land previously granted by their predecessors. Each of these factors were at play when Charles II granted William Penn a charter for Pennsylvania in 1681.

Lord Baltimore’s 1632 charter for Maryland granted him land the length of the Potomac River and northward as far as the 40th parallel. His original charter also included territory that would eventually become Delaware, provided that it had not been settled by people other than Native Americans. Penn’s grant extended from the 42nd parallel southward to the border of Maryland at the 40th parallel. The southern boundary was to be determined "by a circle drawn at twelve miles distance from New Castle, northward and westward unto the beginning of the fortieth degree of northern latitude, and then by a straight line westward. . ."

Two primary issues were at stake. The first to be resolved was whether the settlements along the east side of the Delmarva Peninsula belonged to Lord Baltimore. Procuring access to the Delaware River was of paramount importance to Penn and the success of his colony, therefore he disputed Lord Baltimore’s belief that his grant included the east side of the Delmarva Peninsula because it had been previously settled by the Dutch and Swedes.

The more difficult issue to resolve was whether Lord Baltimore’s northern

boundary should be at the 40th degree of north latitude as accurately surveyed or at the latitude where it was thought to have been at the time that Lord Baltimore received his grant. When Charles II issued Penn’s grant, they both believed that the 40th parallel intersected the circle around New Castle but it was actually located some 20 miles farther north. A compromise was eventually reached in 1732 when a Court of Chancery ruled to establish the line slightly further south than the 40th parallel resulting in a significant loss of land for Lord Baltimore (see lots 1 and 3, Visscher and Franklin). Lawsuits continued to be filed, temporary agreements were negotiated, and attempts were made by the Privy Council to settle the discrepancies between the charters, however the dispute was not settled until 1760 when negotiations were resumed and the controversy was adjudicated in England, largely in Penn’s favor. Three years later Mason and Dixon were hired to sail to America to survey the line.

Charles Mason and Jeremiah Dixon

Determining the precise boundary between the two colonies required expertise beyond that of the colonial commissioners and their survey team. The commissioners, in consultation with the director of the Royal Observatory in Greenwich, chose Charles Mason and Jeremiah Dixon, who had recently returned from an expedition sponsored by the Royal Institute to observe the transit of Venus, as the most qualified to conduct the survey. They arrived in North America in November of 1763 bringing with them the same scientific instruments used to observe the transit of Venus, the most important of which was a zenith sector, a specialized telescope that points directly overhead allowing the astronomer to locate the exact position of the stars necessary to determine an accurate reading of latitude.

Mason and Dixon began their survey by measuring the 83-mile north-south division between Maryland and Delaware known as the "Tangent Line." The 233-mile west line, represented on this manuscript map, was officially ordered by the Boundary Commissioners on June 18, 1765. Mason kept a daily journal, which included mathematical and astronomical data, survey notes, correspondence, and detailed their daily progress. Dixon, who was an experienced surveyor, is likely the one who prepared the map and cartouche. The 364-page journal reveals the extraordinary difficulties the survey team endured, necessitating the use of Native American guides and teams of men to clear sightlines. On October 9, 1767, Mason wrote, "This day the Chief of the Indians which joined us on the 16th of July informed us that the above mentioned War Path was the extent of his commission from the Chiefs of the Six Nations that he should go with us, with the Line; and that he would not proceed one step farther Westward." The running of the west line took fully two and a half years. On September 11, 1768, Mason recorded the last entry in the journal, "At 11h 30m A. M. went on Board the Halifax Packet Boat for Falmouth. Thus ends my restless progress in America."

Mason and Dixon’s survey map

At the culmination of the survey, Mason and Dixon were instructed "to draw and make out from your Minute Books an Exact and true Plan and Survey of the Boundary Lines... you are to sign and deliver the same either to the Commissioners of Pennsylvania or Maryland..." Two maps were prepared — one illustrating the line as surveyed for the Delmarva Peninsula, and this map recording the boundary of the west line. The two manuscript maps were delivered to Pennsylvania Commissioner Richard Peters on January 29, 1768 from which 200 copies were engraved and printed in Philadelphia. This map and numerous other documents pertaining to the Pennsylvania-Maryland boundary dispute were deposited with Pennsylvania Commissioner Benjamin Chew, and remained in the family until they were sold at Christie’s in 1982.

The manuscript map illustrating the eastern boundary of "Three Lower Counties" was donated to the Princeton University Library in 1864. This "West Boundary" manuscript was thought to be lost until 1963 when historians Nicholas Wainwright and Benjamin Chew discovered it among surviving Chew family papers. While comparing this manuscript map of the west line to the engraved versions, he wrote that “Mr. Chew noticed that the cartouche on the strip map differed from that on the other copy. It was soon realized that the strip map, despite its superficial appearance of being an engraving, was actually a manuscript. On Jan. 15, this map was compared at Princeton with the other manuscript part signed by the surveyors. There was no doubt in any of the viewers' minds that both were drawn by the same hand, presumably that of Charles Dixon [sic]. The Princeton part of the manuscript map was acquired by the family of its donor in 1864. No doubt, Benjamin Chew, III, who is known to have given away a set of the map to John McAllister in 1863 (Streeter 32), gave a set to another friend, not realizing that the eastern sheet he selected was part of the original manuscript." (Wainwright, “Tale of a Runaway Cape: The Penn-Baltimore Agreement of 1732” in The Pennsylvania Magazine of History and Biography, V. 87 (July 1963), pp. 288.)