WHOLE BOOKS have been written about some of the participants in the saga of Mason and Dixon’s line, the Calvert and Penn families among them. You can easily find them in libraries. But many of the people (and the instruments!) who played a role in Mason and Dixon’s American adventure have slipped through documentary cracks in the historical record and disappeared. Or perhaps they remain lost in archives, just waiting for an adventure-seeking researcher to find them, like the information recently rediscovered about the Plumstead-Huddle house. However, records that have already come to light offer tantalizing glimpses about what happened to certain people (and instruments) who participated in the survey. Many of these glimpses raise more questions. . . .

CHARLES MASON observed the 1769 transit of Venus, in Ireland, for the Royal Society. (After completing their survey in America, Mason and Dixon did not work together again.) He continued his astronomical work and was highly regarded for creating a set of lunar and solar tables. But he never forgot his time in America. In September 1786, Mason, Mary (his second wife), seven sons, and a daughter immigrated to Philadelphia. Less than two weeks after their arrival, he sent a note to Benjamin Franklin, informing him that he was sick and confined to bed. Sadly, Mason died less than a month later, on October 25, 1786. He is buried in an unmarked grave in Christ Church Burial Ground, not far from the tall steeple he first saw when he entered Philadelphia in 1763. Several Pennsylvania newspapers published his obituary.

JEREMIAH DIXON also observed the 1769 transit of Venus, but in Norway. Afterward, he worked as a surveyor in England. Several years later, he bought a dyehouse, which provided him with additional income. Dixon never married. He died on January 22, 1779, at the age of forty-six. The location of his grave is unknown. In his will, he left the rent and profits of the dyehouse to Margaret Bland, instructing that she use them “for and towards the maintenance, education, and bringing up of her two daughters, Mary and Elizabeth.” The dyehouse was to belong to Mary and Elizabeth when they reached the age of twenty-one. The relationship between Margaret, her daughters, and Jeremiah Dixon is unknown.

MOSES MCCLEAN served as a captain during the Revolutionary War. He became a prisoner of war after being captured by Indians who sided with the British. He remarried after his wife, Sarah — whom Charles Mason had met — died. He and his second wife moved to Ohio. Moses died in 1810.

JOHN HARLAN is reported in the Harlan family genealogy as having drowned in Brandywine Creek. His name ceases to appear in colonial records after 1768.

PHINEHAS HARLAN married his sweetheart, Elizabeth Jones, on September 24, 1766, one year after he worked as an axman on the line.

THOMAS AND HANNAH CRESAP remained loyal Marylanders. By the mid-1740s, Thomas established a fort and trading post along the bank of the Potomac River, in the wilderness of western Maryland, and within a few years built the home Mason and Dixon visited. When George Washington was sixteen years old and participating in a frontier land survey, he spent two nights at the Cresaps’ home. In his journal, Washington wrote that the road to Cresap’s house was “I believe the Worst Road that ever was trod by Man or Beast.” Cresap and his son became land speculators and founded the town of Oldtown. Hannah Cresap died before 1774. Thomas died in 1790; his grave overlooks the Potomac River. Yet his spirit of discovery lives on in the archaeological excavations on the site of Cresap’s fort, where an abundance of eighteenth-century artifacts have been unearthed.

ZENITH SECTOR: Owned by the Penn family, the sector remained in Pennsylvania. It was used to observe the 1769 transit of Venus and to survey the boundary between New York and New Jersey. After the Revolutionary War, the sector was housed in different cities, and eventually put on display in the Pennsylvania state capitol building, in Harrisburg. It was reported as destroyed when the building burned in February 1897.

TRANSIT AND EQUAL ALTITUDE INSTRUMENT: For many years, the transit’s whereabouts were unknown. Then, in 1912, it was found in Philadelphia underneath the floorboards in the bell tower of Independence Hall, formerly called the Pennsylvania State House, the building where Mason and Dixon sometimes met with the commissioners. How the instrument got there no one knows. It is on display in a large meeting room in the hall, possibly the same room where Mason and Dixon first unpacked it in 1763.