Bill Calhoun

 was a member of the Followers of the Apocalypse.

Background
In 2246, he and the future Caesar, a fellow Follower, were sent east to study tribal dialects. He was instructed to meet with a Mormon missionary named Joshua Graham who was a tribal specialist. They embarked on a journey to the region known formerly as Arizona as part of a nine-person expedition.

At some point in 2247, Graham, Calhoun and the future Caesar were captured by the Blackfoot tribe for ransom. At the time the tribe was at war with seven other tribes, a war they were inevitably going to lose. Unwilling to be destroyed along with them, and against the wishes of his companions, Caesar chose to use his knowledge to train the Blackfoot tribe in the art of warfare after witnessing their lack of knowledge first hand. He quickly impressed them enough to the point where he was made their leader, conquering other tribes.

Surprisingly, Joshua Graham decided to join Caesar as his right-hand man, now known as the Malpais Legate. While Calhoun was sent back to the Followers to inform them of what he was doing, the other six members of the expedition were murdered on the self-proclaimed Emperor's orders.

Appearances
is only mentioned in Fallout: New Vegas.