250 years ago Mason and Dixon arrived in Philadelphia and began their survey work

Written by Pete Zapadka on .


What a fascinating period in U.S. history we're commemorating this week. We're pausing to look back, often with awe, on significant events that shaped the nation we know today.
Of course, the appropriate focus is today's 150th anniversary of the famous Gettysburg Address. The address was delivered by President Abraham Lincoln on the heels of the battle on Pennsylvania soil in which tens of thousands of Americans, in armies of the North and South, died.
The Battle of Gettysburg widely is believed to have been the turning point of the Civil War, a bloody dispute in which the Union claimed victory over the Confederacy.
But as a local historian and a long-time amateur astronomer, I'm also aware of another historic milestone with significant roots at this time -- the 250th anniversary of Mason and Dixon arriving in Philadelphia to begin their famous survey work.
Both men were well-versed in astronomy and, in fact, used astronomical observations to draw with astonishing precision their famous border, essentially the boundary between Maryland and Pennsylvania, Delaware and Maryland, and later, Pennsylvania and West Virginia.
The actual anniversary of Mason and Dixon's arrival in Philadelphia was Nov. 15, and the two men began their planning work almost immediately.
In "The Journal of Charles Mason and Jeremiah Dixon, 1763-1768," they reported that on Nov. 16 they had "attended a meeting of the Commissioners appointed by the Proprietors of Pennsylvania to settle the boundaries of the Province." On Nov. 17, they reported they "Wrote to his Excellency Horatio Sharpe, Esquire, Governor of Maryland, signifying our arrival at Philadelphia."
20131119pzmasondixon 01Charles Mason's handwriting in "The Journal of Charles Mason and Jeremiah Dixon, 1763-1768."
During the rest of November, Mason and Dixon spent time inspecting their instruments that, like the survey team leaders, had made a long sea voyage from England. On Nov. 30, the men met "the Commissioners appointed by Lord Baltimore to settle the Boundaries of Maryland came to Philadelphia." 
By Dec 14-15, Mason and Dixon were ready, but unable, to begin their actual survey work because of rain and snow. It was cloudy Dec. 17 and 18, but on Dec. 19, they made astronomical observations of the stars Delta Persei, Chi Ursae Majoris (below the bowl of the Big Dipper) and Capella (the brightest star in the constellation Auriga).
Mason and Dixon first had to determine the southernmost point of the city of Philadelphia -- colonial officials had agreed the boundary line would be drawn 15 miles south of there. Once that point was found, the team moved 31 miles west to a location near Embreeville, Pa., to start the next leg of their work (had they first gone 15 miles due south of Philadelphia, Mason and Dixon would have had to cross the Delaware River and ended up in New Jersey).
From their now-celebrated Star Gazer's Stone near Embreeville, the team surveyed the required 15 miles due south to the latitude of the Mason-Dixon Line.
20131119pzstargazersstone 03Star Gazer's Stone near Embreeville, Chester County, Pa., marking the site where Mason and Dixon did work related to their survey (Pete Zapadka/Post-Gazette)
20131119pzaboutstargazersstone 04 1Historical marker describing the significane of Star Gazer's Stone near Embreeville, Chester County, Pa. (Pete Zapadka/Post-Gazette)
For much of the next four years, Mason and Dixon conducted their survey work, finally halting in October, 1767, atop lofty Brown's Hill, about three miles southwest of Mount Morris, Pa. They were about 22 miles short of their goal -- the present-day southwest corner of Pennsylvania. Unrest among local Native American tribes prompted the survey team to stop.
20131119pzsouthphilly 02A state historical marker unveiled over Labor Day weekend in Philadelphia to mark the city's southernmost point in Mason and Dixon's day (Pete Zapadka/Post-Gazette)
So for the next four years, we'll be celebrating 250th anniversaries of Mason and Dixon milestones. By 2017, there will be events near the Pittsburgh and Morgantown, W.Va., areas, to mark the 250th anniversary of activities on "The Line" in our region. 
Even as history buffs turn their eyes today to the powerful Gettysburg Address, it is important to remember the Mason-Dixon Line actually was drawn about a century before the Civil War. It is a common inaccuracy that the two are related. Find out more about "The Line" beyond the popular misconceptions.
In addition to almost four decades at the Post-Gazette, Pete Zapadka spends time beneath the stars and exploring the western end of the Mason-Dixon Line -- the Pennsylvania-West Virginia border some 50 miles south of Pittsburgh. He operates the website


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