The Jeffersonian Federation did not join the Republic of California on day one. They had left the rest of California on purpose, and did not want to be entangled in their problems. But as the Second Great Depression moved on into the Cybernetic Wars and the Islamic Jihad, they grudgingly accepted that it would be best to have allies. The shattered cities north and south of them were out of the question. But the mixture of inland counties and Indian tribes working to secede from the coastal Californians were Jefferson’s kind of people. If there was anyone they were interested in standing beside, it was those people. So they signed on the dotted line and joined up. I’ll note here that they were never a primary source of men and arms used to defend the Republic, or to attack her enemies, but they became a quiet and efficient ally when they signed up. And they have maintained that quiet competence ever since. Outsiders may worry about gang violence in San Diego, or what a cybernetic freak out would do in Los Angeles, but Jefferson? No man. No troubles ever come out of Jefferson.