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Story  of  The  Mason - Dixon  Line

Information for this article was edited from papers of authors for the

SHS Rendevous 2002 and the book Mason & Dixon  by Thomas Pynchen

The Mason-Dixon Line has a history which dates back to early America. The King of England granted land in the colony of America to the English families of Calvert & Penn. The future of the boundary between these grants proved to be the basis of several historical events. First, it was to become the longest line ever surveyed on the ground. Second, it become recognized as a dividing line in the War Between The States. It now serves as the

boundary for the States of Pennsylvania, Tennessee, Delaware and Maryland.

In 1750, the Court of England established legal steps to settle this boundary dispute. Charles Mason, an astronomer and Jeremiah Dixon, were appointed to  resolve this dispute. A series of circumstances delayed the start of the survey until 1763. These persons were recognized experts who had just completed the task of observing the Transit of Venus. By their selection, Charles Mason and Jeremiah Dixon not only resolved this disputed boundary; but, become famous in the process. 

The legal and court findings for this boundary resolved the issues. This clarification and other guidelines from the court provided Mason and Dixon the information necessary to finally survey this boundary line.

Below are a few of the major points decided by the court in 1750:

              "Commissioners of the court decided the courthouse in New Castle to be"

                            1. The center of the circle and center of New Castle.

                            2. Circle was to have a 12 mile radius

                            3. Lower parallel to be as shown on a map affixed to the Articles of Agreement of 1732.

                            4. Northern boundary of Maryland to be 15 miles south of Philadelphia.

                            5. Work to be completed by April 1752.

When Mason & Dixon arrived in 1763, they brought with them the most modern equipment possible. The instrument has been built by John Bird, the most accomplished instrument maker in England.  On  December 6, 1763, they set up an observation location to determine the latitude for the southern point of Philadelphia. After determining this point, they measured 15 miles south and established the necessary points to locate the circle and the beginning location. The "Post Mark'd West" was established at latitude 39/43/17.4.

On June 26, 1764, they started running the tangent line for the westward boundary. Work on the disputed line had finally started! Granite markers brought from England were placed points along the line. A rectangular marker was placed every mile and a "Crown Stone" marked with the family crests were placed at , the Surveyorsfive (5) mile intervals.

In 2002, the Surveyors Historical Society (SHS) replaced a  missing mile stone (marker 85).  They  placed the new Crown Stone   using the same methods and procedures a Mason & Dixon.

During the period December 17, 1765 and November 20, 1766, markers had been placed for approximately 233 miles. Yet the line was not complete, Native Indians  told them "white man, you have gone far enough".


The boundary line produced by Mason & Dixon developed  methods to survey lines of great length on earth's surface. They had used short segments to define points on the Great Circle and developed a procedure for making astronomic observations along a straight line. They had made these observations at 12 mile intervals and remeasured each segment after correcting the . When completed, Mason & Dixon were satisfied their line was within a fifty foot band of being straight.

Modern science now allows us to determine with a greater degree of accuracy the work of Mason & Dixon. These results determine that they did not achieve the fifty foot standard. Unknown at the time, gravity and mass have an effect on the vertical of the plumb bob. When a correction is applied for this scientific determination, Mason & Dixon's point would be closer to their stated position. 

In summary, Mason & Dixon's work would become the Maryland-Pennsylvania boundary. It's name is one of the most respected lines in America and their line has served as a divide between the northern states and the southern states. Their line is now monitored by "The Mason-Dixon Preservation Society", who protect and preserve the markers along this historic boundary. The Mason-Dixon Line, even though produced by the English will forever be remembered in American History!

We trust you found this information interesting.

You are invited for a visit to the museum.

Jefferson and the east Texas area is a great tourist destination.


We hope your plans include a visit.

​​​​​​​​​​​​Museum Of Measurement And Time