Horry was born and raised in the Prince George Winyah Parish (Georgetown, South Carolina and vicinity[2]), as were both of his parents and all four of his grandparents.

[3] Taught to read and write at the Indigo Society school near his home in Georgetown, Peter Horry later served a harsh apprenticeship with a local merchant.

By the late 1760s Horry had established a mercantile partnership in Georgetown, which he discontinued after inheriting 475 acres from his father to become a plantation owner.

[2] He presumably thrived in this new role, as he later purchased his brother's share of his father's estate, a rice plantation called Belle Isle.

After the appointment of Lieutenant-Colonel Francis Marion, another officer of the South Carolina Line without a command—his regiment having been captured at the Fall of Charleston while he was on furlough—to be brigadier general of the lower brigade of the militia of South Carolina by Governor Rutledge, Horry became colonel of one of the militia regiments under Marion.