In occasional outcroppings and beneath the surface of the high plateaus and just west of the southern Rocky Mountains are large deposits of sub-bituminous coals. These coals were formed in the estuaries, swamps, and lagoons at the edges of the extensive epicontinental sea of the Late Cretaceous Period. Many millions of tons of this coal lie strippable depths (overburden is less than 250 feet), but perhaps 90% of the total deposits lie deeper. These deposits will probably only be tapped if underground gasification proves feasible. In this paper the question of the suitability of Southwestern coals for underground gasification is examined.