Gannon Senior was an Enclave officer after the destruction of the Oil Rig. After his death in combat, his family tried to integrate into the NCR, but they ended up settling in the Mojave Wasteland. He has a son named Arcade.
Gannon Senior was an Enclave officer who was stationed at Camp Navarro, and led an elite unit called the Devil's Brigade. Himself, Cannibal Johnson, Judah Kreger, Orion Moreno, Doctor Henry, and Daisy Whitman composed the brigade.
He wore a prototyped model of the advanced power armor Mk I imbued with Tesla coil technology during his last mission, which would later be passed down to his only child Arcade Gannon as a family heirloom.
Gannon Senior is mentioned in Fallout: New Vegas.