Th e Epic Survey of Mason and Dixon Two hundred and fi fty years ago, a pair of English surveyors came to the New World to resolve a fi erce boundary dispute. The result was an incredible scientifi c and engineering achievement. Reprinted with permission from the March 2014 issue of PE magazine, published by the National Society of Professional Engineers 15 Professional Land Surveyors of Oregon | www.plso.org THE EPIC SURVEY OF MASON AND DIXON By David S. aler, P.E., F.NSPE More than two centuries ago, two English surveyors arrived in America to help settle a long-raging boundary dispute between the colonial proprietors of Maryland and Pennsylvania. Charles Mason and Jeremiah Dixon’s epic fi ve-year eff ort was the fi rst geodetic survey in the New World and would turn out to be the greatest scientifi c and engineering achievement of the age. Th eir story begins with Sir George Calvert, who was the secretary of state to King James I of England. For his loyal service to the crown, he was given the title of Lord Baltimore and granted land in the Americas, which he named Maryland in honor of Queen Henrietta Maria. Th e royal charter granted Lord Baltimore all the territory from the Atlantic Ocean “unto the true meridian of the fi rst fountain of the River Potowmack” and from the south bank of the Potomac River to include all land “which lieth under the Fortieth Degree of North Latitude.” Th e other players in this drama were members of the Penn family. Sir William Penn had been a distinguished admiral in the Royal Navy who had loaned the profl igate King Charles II the then-stupendous sum of 16,000 pounds sterling. In exchange for discharging the debt, his son, also William, was granted the province of Pennsylvania. Penn’s charter granted the land from the 42nd parallel of latitude down to the 40th parallel, excluding a 12-mile circle around the town of New Castle in what is now Delaware. So Calvert, the proprietor of Maryland, was granted from the Potomac up to the 40th parallel and Penn, the proprietor of Pennsylvania, received from the 42nd down to the 40th parallel to where it intersected a circle, 12 miles from New Castle. But the question was, “where was the 40th parallel?” Unfortunately for the proprietors, the maps at the time were based on the exploration of the Chesapeake region by Captain John Smith in 1608, and the Smith map showed the 40th parallel too far south. In fact, the 40th parallel of north latitude does not intersect a 12-mile circle around New Castle but lies much farther north. It was this discrepancy that set off the granddaddy of all boundary disputes, which raged for more than 80 years. Th e dispute was so bitter because the stakes were high. Th ere were about 4,000 square miles of territory in question, and Philadelphia, which had been settled at the limits of » continues on page 16 » MS 174, DOCUMENT 1051 MASON DIXON MAP Mason-Dixon Map. Credit: Maryland Historical Society
PLSO Issue 1 2015 Jan_Feb
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