A family of related gas-volcanoes is proposed which includes the tiny and unusual Papago Buttes in greater Phoenix, AZ, the much larger Mt. McDowell structure some 35 km east of Pheonix and the giant Absaroka volcanoes in western Wyoming and southern Montana. A gas-volcanic solution to the relatively simple Papago Buttes is given and then extended to include the further developed and more complex Mt. McDowell. Finally, the theory is projected to the very complex Absaroka volcanoes.