The Baja is a location within the New California Republic.
Background
The Baja California peninsula is a peninsula in what was northwestern Mexico. Its land mass separates the Pacific Ocean on the west from the Gulf of California (or "Sea of Cortés") on the eastern coastline. In 2281, under orders from President Kimball, New California Republic Rangers were deployed to the area for what Chief Hanlon describes as "chasing ghosts"(perhaps refering to Enclave remanants). As the game progresses, several rangers are moved to the Mojave Wasteland from here. If you talk to some NCR Troopers, they sometimes will say "I heard the ranger vets are from baja, i've never seen one before, but I heard they chew nails and spit napalm.
Appearances
Baja is mentioned in Fallout: New Vegas.