Gillespie's paper trail begins on December 1, 1740, when 'Thomas Glassbey' purchased 400 acres in northern Augusta County, Virginia, in a draft of the Shenandoah called Long Glade. The forty-shilling deed is the first document that places him anywhere. Sometime before 1750, Thomas, his wife Naomi, and their young son James moved south to Anson County, North Carolina. By tradition they were the first European family to settle west of the Yadkin River in that part of the colony. The land they reached was Catawba and Cheraw territory, and their settlement was part of a Scots-Irish migration that would, within a generation, transform the Carolina backcountry. By the time Rowan County was carved out of Anson in 1753, the Gillespies were established on Sills Creek with a Granville Land Grant in hand.

By his death in 1796, Gillespie owned around 2,570 acres in Rowan County alone. His plantation house had more than five rooms. He owned a cotton gin, raised flax and wheat, kept horses and cattle. None of that infrastructure would have existed without the work of the people he enslaved. Census records identify seven; his will identifies six by name. In a county where 1,742 enslaved people lived among 2,432 households in 1790, Gillespie's holdings placed him squarely within the planter class that built the regional economy on coerced labor. The crops they cultivated, the structures they maintained, and the children they raised in slavery are the foundation of every later achievement attributed to the family. Their names, mostly absent from the surviving record, deserve the search.

Gillespie was an early elder at Thyatira Presbyterian Church, founded by 1750 on Cathy's Creek and the oldest Presbyterian church in this part of western North Carolina. Religious life and political life ran together in the Scots-Irish settlements. When the Revolution came, Gillespie served as a commissary in the Rowan County Regiment, one of five commissaries under Quartermaster General Joseph Marbury, responsible for provisioning a brigade of roughly 1,400 to 2,000 men. The work was unglamorous: requisitioning grain, securing salt, finding wagons. For his service he received land grants totaling roughly 6,000 acres on Flat Creek and the Duck River in what became Tennessee in 1796, plus parcels in Washington and Greene counties along the Nolichucky and Clinch rivers. His sons would eventually claim that land.

Gillespie's daughter Lydia married Captain James Knox. Their daughter Jane Gracey Knox married Samuel Polk. Their son was James Knox Polk, eleventh President of the United States, who annexed Texas, fought a war with Mexico, and added the territory that became California, Arizona, New Mexico, Utah, Nevada, and parts of Colorado and Wyoming to the United States. Thomas Gillespie did not live to see his great-grandson born; Polk arrived in 1795, the year before Gillespie's death. But the family fortune that gave Polk his start was built on land granted to Thomas, and that land was made productive by the enslaved laborers whose names history mostly failed to record. The presidential line is real. So is the cost.

Thomas and Naomi Gillespie died on the same day: December 13, 1796. Thomas was 78, Naomi 69. According to their memorial at Thyatira Presbyterian Church, they had been married 51 years. Six of their sons carried them to their place of interment, where they were laid in the same coffin. The shared grave is one of the more striking artifacts in a cemetery full of Revolutionary-era markers. The Thyatira churchyard also holds Thomas's father-in-law John Knox and the older generation of Cowans, Brandons, and Locks who built the country's first inland Presbyterian society. The Gillespies are not the only family there whose wealth depended on slavery. They are simply the family whose lineage runs through the White House.