Greg Alexander

The Mason-Dixon Line’s real origins

Mason-Dixon Arrive, March 2004

Most people know that the Mason-Dixon Line separates Maryland from Pennsylvania, but if you ask people what they think of first when you say, “Mason-Dixon Line,” many will say, “slavery,” as in the Mason-Dixon Line separated the free states from the slave states during the Civil War. However, the origins of the Mason-Dixon Line have nothing to do with slavery and predate the Civil War by more than 200 years.

The origins of the line actually begin way back in 1632 when King Charles I of England gave the first Lord Baltimore, George Calvert, the colony of Maryland. Fifty years later, King Charles II gave William Penn the land to the north of Maryland, which later became Pennsylvania, and in 1683, he further gave Penn land on the Delmarva Peninsula that included the eastern part of Maryland and Delaware. Due to the fact that Calvert and Penn received their grants by different kings, the language in the grants did not match and confusion arose as to what land Calvert and Penn owned. The two families took the matter to the British court, and the chief justice decided that the boundary between Maryland and Pennsylvania should lie 15 miles south of Philadelphia. In 1860, the two families decided that a new boundary should be marked. Unfortunately, there were no surveyors in the colonies that could handle this difficult task, so two experts from England were hired.

Charles Mason and Jeremiah Dixon — who had worked as a team before; Mason as an astronomer and Dixon a surveyor — were sent to Philadelphia in 1763 to tackle the job of marking the boundary. Mason and Dixon — after first determining the exact location of Philadelphia — set out to mark the line by laying stone markers to indicate the boundary. A continuous line of latitude was the goal, and Mason and Dixon used the stars to chart their path through the rugged terrain. The task was enormous — Mason and Dixon were responsible for marking a 233-mile-long boundary line between Pennsylvania and Maryland and the 83-mile-long line between Maryland and Delaware. The process took five years.

“What they were able to do is simple amazing, especially considering the instruments that they were using and the conditions they were battling,” says Todd Babcock, president of the Mason-Dixon Line Preservation Partnership (MDLPP). “To be able to mark a continuous line of latitude this precisely gives testament to their brilliance. There is some discrepancy along the line due to gravity’s effect on the equipment that they were using, not miscalculations by Mason and Dixon,” Babcock stresses.

Besides the enormous amount of territory that Mason and Dixon had to cover, the conditions they battled were tough, says Babcock. “First there was the terrain. They battled hills, marshes and rough land. Secondly, there was the weather with temperatures well below zero. Also, remember that this territory was not safe; it was very hostile,” says Babcock. “In 1763, 25 Native Americans were massacred near Lancaster, Pa., by locals, and here are Mason and Dixon living and working in this area trying to haul around massive pieces of limestone to mark the Line.”

The Mason-Dixon Line was marked with limestone markers with designs on each side depicting what side was Maryland and Pennsylvania. Over time, these markers have been damaged by weather, age and vandalism, so Babcock and others gathered together in November 1990 to discuss what could be done to save the markers. “Some surveyors in Maryland and Pennsylvania were concerned about the conditions of the stones, and 16 of us gathered together to brainstorm to see what could be done. We decided first to conduct an inventory,” Babcock says. “We started with the 132 miles of the Mason-Dixon Line that are marked with limestones. We photographed them, described them and took inventory. We’ve located 200 of the 230 stones that separate Maryland and Pennsylvania.” Babcock says that assigning GPS coordinates was crucial. “The location of the stones is more important than the stones themselves. The location of the stones gives us the exact boundary and shows the hard work of Mason and Dixon.” Babcock says that the organization has purchased granite stones to replace damaged or missing stones.

The association with the Mason-Dixon Line and the debate over slavery originates with the Missouri Compromise of 1820, which established a boundary between the slave states of the South and free states of the North. The Mason-Dixon Line was used as the eastern origination point and the free/slave state dividing line then went west. Babcock notes that the confusion over the Line’s association with slavery is troubling. “The Mason-Dixon Line had nothing to do with slavery, and actually it didn’t separate the slave and free states. Maryland, which lies to the south of the line, had slaves but remained in the Union. Delaware also had slaves but stayed in the Union. I feel as though Mason and Dixon’s hard work gets lost in history due to this misconception.”

Babcock adds that — although it was not the original intent of the MDLPP — the organization has aided in the effort to better educate people about the real origins of the Mason-Dixon Line. “It wasn’t one of our original objectives, but we now have a CD with our report and have collected papers and books on the origination of the Line, scanned them and put them in PDF format on the CD to better educate the public.”

Although it’s been a long process to document the location of the Mason-Dixon Line and the markers, Babcock says it’s worth it. “These two men and their techniques were well ahead of their time. I’m just happy to be a part of their work.”

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