Ashton, Virginia

is the location of Idlewood, the secure facility where living gammas are held. We first learn of it in episode 1x03, "Dexterity".

Ashton does not show up on Google Maps (this URL shows Ashton, West Virginia). It may be a cryptomunicipality, but the Powers That Be (specifically Will Shetterly ) were their typical unhelpful selves when asked.