Jim Shomper talks like a star of “Law & Order.” With a booming voice and a knack for delivering one-liners, Shomper acts like a regular on the long-running television show.

For the past several years, Shomper also has walked a beat as he helped search for the site of the Plumstead Huddle house, which Charles Mason and Jeremiah Dixon determined was the southernmost point in Philadelphia when they started their famous survey 250 years ago.

The house is long gone, and finding the original location was not easy. But after sifting through a trove of maps, deeds and other documents, Shomper and many others finally discovered the starting point for the survey of the Mason-Dixon Line.

“It’s a detective story,” Shomper says. “Surveying is a detective story.”

More than 200 people, from as far away as Australia and the United Kingdom, attended the 17th annual Surveyors Rendezvous on Aug. 29-31 in Philadelphia and eastern Pennsylvania. Three ceremonies highlighted the event: one at the Star-Gazer’s Stone; one at the southernmost point in Philadelphia; and one at Christ Church Burial Ground, where Charles Mason was laid to rest. The event also featured educational sessions, covering topics such as colonial surveying in Pennsylvania and the depiction of surveyors in movies and television shows. The Surveyors Historical Society, one of the sponsors of the Rendezvous, also held its annual banquet where a David Rittenhouse reenactor addressed the crowd.

The ceremonies, though, served as the centerpieces of the Rendezvous in Philadelphia, with each peeling back layers on the history of the Mason-Dixon Line. At the Star-Gazer’s Stone, located in Chester County, Pa., about 31 miles west of Philadelphia, attendees drove in an iron spike to mark the site where Mason and Dixon performed their astronomical observations for their famous survey. “The line they set from the stars,” says Chas Langelan, the vice chairman of the Surveyors Historical Society.

From the Star-Gazer’s Stone, Mason and Dixon began measuring 15 miles due south the boundary line between Maryland and Pennsylvania. “To understand what they did, you have to understand how they did it,” says Todd Babcock, the chairman of the Mason and Dixon Line Preservation Partnership who helped organize the Surveyors Rendezvous with Langelan and Shomper.

Through research, Babcock realized the stone was not at the location of Mason and Dixon’s observatory.  He surveyed the property near the Star-Gazer’s Stone and Harlan House (where Mason and Dixon stayed while they made their astronomical observations), looked through the surveyors’ original field notes and used modern technology such as GIS to determine that the actual point was 745 feet south of the stone in the middle of a nearby road.

  Meet Me in Mobile

The 18th annual Surveyors Rendezvous will take place Sept. 17-20, 2014, at the Admiral Semmes Hotel in Mobile, Ala.

The event will feature Andrew Ellicot’s survey of the 31st parallel, the “Line of Demarcation” between the United States and Spain as specified in the 1796 Treaty of
San Lorenzo.

For more information, go to

Tasked with establishing the boundary for Pennsylvania, Maryland and Delaware, Mason and Dixon worked from three points: the middle point of the Eastern Shore of Maryland; a 12-mile circle around the courthouse steeple in New Castle, Del.; and the southernmost point of Philadelphia, which had to be established from the stars. “The first thing they did when they hit Philadelphia, go find the southernmost point,” Langelan says. “They found the house that was the southernmost house in Philadelphia, built an observatory, did latitude and longitude observations—which took six weeks—established a lat and long of the southernmost point of Philadelphia, and from that latitude measured 15 miles south using measuring poles and 66-foot gunter’s chains.”

“They met with the commissioners and the mayor and the alderman, and they settled on the house of Joseph Huddle that was occupied at the time by Thomas Plumstead as the location that would be the southernmost point of Philadelphia,” Babcock says.

Everyone agrees that Mason and Dixon used the Plumstead Huddle House as the southernmost point in Philadelphia, but where, exactly, was the house? A publication 50 years ago celebrating the 200th anniversary of the Mason-Dixon Line suggested that the Plumstead Huddle house sat at No. 30 South Street, but that didn’t pass the smell test for Shomper, a Philadelphia native who worked as a surveyor in the city for 36 years.

“There was never a reference to the address in any of the official, primary journals,” Shomper says. “It was the Plumstead-Huddle House. I don’t know where the address reference came from, but it was wrong. There’s books and people around that say that it was at the corner of Second and Market, which is even a block farther west. That’s wrong. If you’re familiar with the city, you know where approximately it should be. Now eliminating it down to a smaller, reasonable error of where he lived was the hard part.”

Numerous people, including students from Penn State-Abington, teamed up to tackle the investigation. They sifted through documents in the Pennsylvania State Archives, Pennsylvania Historical Society and the Philadelphia Contributionship, which started as a fire insurance company in 1752. “The key was finding some of the old documents and eliminating other possibilities,” Shomper says. “It was more a case of elimination than finding things.”


A fire insurance application turned out to be a key clue. Though the document was not a survey of the property, it did have the owner’s name, which gave the investigators names and a timeframe. The insurance document and deed for the Huddle house was found by Torben Jenk, a researcher from Philadelphia.

From there, students combed through the archives, and every time they found a deed with the name Plumstead or Huddle, they examined it to make sure their houses were on different streets. By a process of elimination, they eventually could determine the house’s location. “(Through) my connections with the surveyor bureau and my expertise surveying in the city, I put the modern survey points together with the old, antique records and made the correlation so that we could identify, within reason, of where it is,” Shomper says.

Where was the Plumstead Huddle House? Right in the middle of Interstate 95. “Before we started I knew it had to be in 95,” Shomper says. “I used to commute to south Philadelphia when I worked in that district before 95 was built, and I used to drive up South Street when South Street came down to Delaware Avenue. I knew South Street went all the way through, and it had to be down in that area.”

Although Shomper joked about putting a marker in the interstate in the middle of the night, he instead drove a nail into a pedestrian bridge crossing I-95 near the original location. A few feet from there, at the corner of Front and South Streets, the Surveyors Rendezvous dedicated a Pennsylvania historical marker to memorialize the starting point of Mason and Dixon’s survey. “The location was destroyed by the construction of Route 95 and other construction throughout the years,” Babcock says. “Unfortunately the house is no longer there, but this is as close as we can get with the sign.”


A few blocks away and in the shadow of Independence Hall sits Christ Church Burial Ground, where Mason was laid to rest in an unmarked grave in 1786. Though officials at Christ Church do not know the exact location of his grave, the cemetery believes he was buried near the grave of Tench Coxe, who was the church warden.

The final day of the Surveyors Rendezvous concluded with a ceremony dedicating a memorial stone in Mason’s honor at Christ Church Burial Ground. A plaque rests in front of the stone, an original boundary marker on the Mason and Dixon Line, on the main path of the cemetery.

Langelan says it is important to remember Mason and his contributions. Though the work he and Dixon did determining the boundary between Maryland and Pennsylvania was not perfect—the original stones do not all sit on the same line of latitude and some were separated by more than a mile—they still exceeded the accuracy specifications of the instruments they used. “It’s to this day the most remarkable boundary survey of its type ever conducted by anyone anywhere in the world,” Langelan says.

Furthermore, the lessons of Mason and Dixon are long-lasting. Babcock says the techniques he used to investigate the Star-Gazer's Stone carry over into professional surveying today, and Shomper points to even more fundamental reasons.

 “It’s only the surveyor that can take the piece of paper, interpret it and put marks on the grounds so people can say this is where I live, this is what I own, this is where my mother was, this is where my father was born,” Shomper says. “It’s very important to do that. There’s no technology. GPS, yeah, if you have coordinates, but how do you get coordinates for a 200-year-old deed? You can’t invent them, you can’t just write them up, you’ve got to go out there. It’s a tangible thing, and people are comfortable with that.”