Because of the Blackwater massacre, Arthur can't travel to Great Plains and Tall Trees. But why isn't that the case with Big Valley? It is also a part of West Elizabeth. Realistically, shouldn't the entire state be marked red in the map with "Wanted: Dead or Alive?"
Also, I also noticed how no gang member other than Arthur, Micah, Lenny, Javier and Charles steps foot in West Elizabeth in 1899 because of their wanted status. Not even in Big Valley which isn't supposed to be the wanted region.