Gabriel Long was born to Nimrod Long and his Ellen Williams in 1720 in Culpeper County, Virginia. He was of strong Irish stock and of direct descent from the Longs of Wraxall. He came of age during the French and Indian War, in which his father and grandfather were both heavily involved, and he tasted war for the first time in it as a color-bearer and private soldier in the state militia. Long grew to be an excellent marksmen and horse rider and into the frontier soldier he would later become.