On October 18, 1767, Charles Mason and Jeremiah Dixon completed a four year project that was designed to end a bloody border dispute between the colonies of Pennsylvania and Maryland. Using astronomical devices, (One called the Zenith Sector was designed especially for the project) and precision surveying instruments, they set out to define the boundary between the two colonies. They were also contracted to survey the boundary between Delaware and Maryland, which is part of the Mason-Dixon Line, but today, it is mostly overshadowed by the Pennsylvania line.

Mason-Dixon Line
Approximate Location of the Mason-Dixon Line. Right-click to view the entire map.

The line was set from a point 15 miles south of Philadelphia and headed 243 miles west to a point that is between Pennsylvania and modern West Virginia. Every mile along the line, the Mason and Dixon crew placed large, cube-shaped stones with a P engraved on one side and an M on the other. Every fifth stone, in the shape of an obelisk, spelled out the names of the colonies and also bore the coats of arms. 241 years later, many of the stones are missing, but many are still there.

Mason and Dixon faced uncountable obstacles, marshes, mountains, rivers, weather and hostile natives, not to mention hostile colonists, but laid out the line in a four year project. It remains a monumental feat.

Two modern day surveyors, Todd Babcock and Dilwyn Knott, began to document the line in 1992. Armed with modern surveying tools and a GPS (Global Positioning System) receiver, they went looking for the stones laid by Charles Mason and Jeremiah Dixon. Some were surrounded by iron fences, some had sunken into the earth, some were stolen or otherwise missing, most were badly deteriorated and some were damaged as a result of target practice. Each stone weighed between 300 and 500 pounds, so lifting one and taking it away was no small feat. (Today, many of the extant markers are on private property, so if you want to see any of the markers, you might want to avoid getting a butt full of buckshot and look for the ones that have public access. There is a link at the end of this post.) They actually found one that was long ago reported missing - by using their calculations of where the stone should be, they went digging in a plowed field and located it well below grade.

While the effort of Mason and Dixon was a monumental feat, Babcock and Knott’s accomplishment of finding the markers is no small feat, either. They seem a little embarrassed that their project of locating and documenting the line took far longer than the original surveying took. “It’s a hobby for us, they got paid,” one of them said to the National Geographic.

The Mason-Dixon Line is the traditional dividing line between slave and free states, the demarcation of southern and northern states, and the punchline of an old joke that calls it the boundary between “Y’all” and “Youse guys.” It is still a most interesting piece of American Colonial history.

There is an excellent website about the line and their project out there, it is a little hard to find unless you follow this link: Mason Dixon Arrive Magazine. You’ll find information about Babcock and Knott and photos of the markers.