52 Ancestors 2025: Siblings - The Cossart Family’s Diverging Journeys

 

There are many families in my family tree, and except for recent generations, there may not be many interesting sibling stories that have been passed down. However, one family intrigued me because its various siblings took dramatically different paths.

My 5th-great-grandparents, Francis Cossart and Margaret Van Nest, came from Huguenot-Dutch families in New Amsterdam and later New Jersey. Before the American Revolution, they settled in the Low Dutch Colony of the Conowago Valley in York County (now Adams County), Pennsylvania. They had seven recorded children, and here are the stories of three of them.

Francis was an important member of the community. Before the Revolution, he served on the Committees of Correspondence. During the war, he worked to supply soldiers with clothing and, as a member of the Provincial, then State, Assembly, helped draft the first Pennsylvania Constitution.

David Cossart (1743–1823)

The eldest son, David, followed in his father’s footsteps, serving in the local militia during the Revolution and later in the Pennsylvania Legislature. Even before the war, he had purchased a farm near his family’s land and remained in the area for the rest of his life. His son Denis moved westward to West Virginia, and that branch of the family found great success. One descendant, Robert Cassatt, made a fortune in land and stock trading in Pittsburgh before relocating to Philadelphia. His children became famous: Mary Stevenson Cassatt, the renowned Impressionist artist, and Alexander Johnston Cassatt, president of the Pennsylvania Railroad.

Christina Cossart Clopper (1755–1801)

Christina married Cornelius Clopper, a fellow member of the Low Dutch Colony, and they divided their time between Pennsylvania and Maryland. Their son, Francis Cassatt Clopper, bought a gristmill in Gaithersburg, Maryland, along Seneca Creek. He married an Irish Catholic woman and donated land to the local diocese to build St. Rose of Lima Church. His prominence led to the Baltimore & Ohio Railroad building the Metropolitan Branch to serve the D.C. and southwestern Maryland region. The road passing his mill, Clopper Road, later inspired lyricists Billy Danoff and Taffy Nivert, from Gaithersburg, to write that song that was completed by John Denver. Interestingly, this branch of the family also began using the “Cassatt” variation of the surname.

Pieter Cossart (1746–1781)

The second son, Pieter (Peter), was also a Patriot and militia member. Unlike his siblings, who remained in the east, he was drawn to the west, lured by the promise of land in Kentucky. In 1781, he migrated with many in-laws to the Fort Harrodsburg area of the Bluegrass region. Tragically, he was killed by Native Americans within six months of his arrival. His descendants, including Hendrick, William, and David, became farmers, shaping my lineage. His choice to move west remains one of the great “what ifs” of my ancestry. Interestingly, some of his descendants also adopted the “Cassatt” variation of the surname, suggesting that family ties transcended the distances as their paths diverged.

52 Ancestors 2025: Challenging - Mary Nailor

My challenging ancestor is my 3rd-great-grandmother, Mary Nailor Cossairt. In 1814, she married my paternal-line ancestor, Hendricks (Henry) Cossairt (or Cossart) in Franklin County, Indiana. They eventually settled in Warren County, Ohio, where Mary gave birth to about six children. She died on July 15, 1843, and one source lists her birth year as 1782.

What’s the significance? What’s the challenge? Until her marriage, the Huguenot Cossart family had remained within their blended French, Walloon, and Dutch colonies, starting with the founding of New Amsterdam. They kept together through migrations from New Amsterdam to New Jersey, Pennsylvania, and Kentucky. Pioneer life in Kentucky during the American Revolution was difficult (another challenge), and parts of the family moved north to Ohio. There, they began marrying settlers whose families had emigrated from England, and it’s less clear where these English families originated.

Mary does not appear as herself in any of the early censuses, so where should I look? How could I make something of the scant data? I turned to ChatGPT, feeding it all the information I had—her name, marriage, and death—and let it generate probabilities, leads, and directions. I was able to input information about her first- and last-born children, along with checkboxes from the pre-1850 census records. ChatGPT also prompted me to check later census records (such as the 1880 census) for her children’s details, specifically for their mother’s birthplace.

I discovered another Nailor in the same county in Indiana where Mary was married, as well as another in Warren County, Ohio.

Thanks to ChatGPT, I was able to flesh out more details: Mary Nailor was born around 1792 in Maryland and migrated west before 1814, possibly through Kentucky. She married Henry Cossairt on December 12, 1814, in Franklin County, Indiana, and the young family settled in Warren County, Ohio, where Henry bought a substantial farm in 1821. Mary had six children and died in 1843, around the age of 51. One possible brother, John, about two years older than Mary, lived in Franklin County, Indiana.

The value of ChatGPT lies in its ability to analyze multiple bits of disparate data—such as the early census age/sex checkboxes—and generate plausible conclusions (or dismiss implausible ones) while pointing me in the right direction.