For additional meanings of "McPherson", please see McPherson.
McPherson was a genetically-engineered Augment from Earth's late 20th century, a follower of Khan Noonien Singh and survivor of the Eugenics Wars. McPherson escaped Earth aboard the SS Botany Bay.
In 2267, the Botany Bay was discovered by the USS Enterprise, where McPherson was among the 72 surviving members of Khan's original group of 84. McPherson was exiled to Ceti Alpha V with the rest of Khan's people after a failed attempt to capture the Enterprise. (TOS: "Space Seed")