Abstract The oil district of Archer County consists of numerous small pools producing from sands in the Cisco (Pennsylvanian) at depths ranging from 900 to 1,700 feet. The oil produced ranges from 390 to 40° Be., and drilling costs are low so that the area has been a profitable one, especially to independent operators. Production in the county is now about 25,000 barrels daily. Oil is found in lenticular sand bodies which have been deposited on the axes of relatively low structures. The occurrence of sand on these high areas and its absence in the synclinal areas is thought to be due to a shallow sea advancing over a series of low folds which were partly represented by topography. Such conditions are thought to be sufficient to cause material to be eroded from these low hills, and sand and heavier material to be re-deposited in shallow water (along the high parts) while fine sand and silt would eventually sink in the deeper water. The presence of shale containing land plants overlain by a marine sand in the producing zone indicates that the oil is indigenous to the producing horizons.