This unnamed survivalist organization was founded by Russell Otto and an unknown number of other people.
At some point long before the apocalypse, this organization was founded by Russell Otto, his family and an unknown number of other people. It was preparing for the fall of the democratic form of government. It can be implied that, given the nature of catastrophe they were preparing for, that they were heavily armed and had a base of operations. Their main base of operation appears to be Broke Jaw Ranch.
Various members of this group were encountered by the dispersed members of Madison's Group. They appeared to be heavily armed and have access to military vehicles, as seen in the promotional image for Season 3 where Jake Otto et al are seen standing in front of a Humvee painted in desert camouflage.