Mellon was born to farmers Andrew Mellon and Rebecca Wauchob on February 3, 1813, at Camp Hill Cottage, Lower Castletown, parish of Cappagh, County Tyrone, Ireland now Northern Ireland.
Mellon wrote in his autobiography that at the age of ten, he had been struck by "wealth and magnificence I had before no conception of" upon viewing the mansion of prominent landowners Jacob Negley and Barbara Ann Negley [REF].