In the Western Coal Field region of Kentucky, water is obtained from consolidated sedimentary rocks of Mississippian and Pennsylvanian ages and from unconsolidated sediments of Cenozoic age. Pennsylvanian rocks crop out in more than 95 percent of the area and consist of shale and sandstone interbedded with some limestone and coal. The Pennsylvanian strata are divided into five formations. They are, in ascending order: the Caseyville sandstone and the Tradewater, Carbondale, Lisman, and Henshaw formations. The Anvil Rock sandstone member of the Lisman formation and the Caseyville sandstone are the only bedrock aquifers in the region that are known to yield more than 100 gpm (gallons per minute) to wells. Most bedrock wells produce enough water for a modern domestic supply, more than 500 gpd (gallons per day), and few yield so little water as to be inadequate for hand pumps and bailers, less than 100 gpd. Unconsolidated Cenozoic deposits range from latest Pliocene(?) to Recent in age and consist of clay, silt, sand, and gravel. High gravels, tentatively considered to be late Pliocene and early Pleistacene in age by McFarlan (1950, p. 125), and loess of Pleistocene age are locally exposed, but nearly all of the alluvium is of late Pleistocene and Recent ages. The alluvium along the Ohio River generally yields from a few hundred to as much as 1,000 gpm to single vertical wells and as much as several thousand gallons per minute to wells that have multiple horizontal screens. Alluvium in the tributaries of the Ohio River generally is finer grained than that of the Ohio Valley. The highest known yield from a well in the alluvium of the tributaries is 56 gpm; other wells yield enough for domestic supplies. Availability of ground water in the region depends on the character and thickness of the aquifer penetrated, and, where the aquifer is bedrock on the depth of the water-bearing bed, and to a certain extent on the topographic situation. Most bedrock aquifers in the Western Coal Field region are sandstone and may vary greatly in thickness and composition within short distances. The region is divided into five areas of ground-water availability. Area 1 is confined to the Ohio Valley, most of which is underlain by relatively thick sections of sand and gravel that yield at least 50 gpm to most wells at depths of less than 150 feet. In area 2 most wells yield enough water for a modern domestic supply from depths of less than 300 feet. This area includes the largest part of the bedrock outcrop in the region, some of the alluvial area along the Ohio River, and much of the alluvial areas along the larger tributaries. In area 3 most wells yield enough water from depths of less than 300 feet to supply domestic needs when a hand pump is used. This area covers the bedrock parts of the region that are underlain by shale, sandy shale, and limestone, and the section where few wells are known to yield large supplies of water. In area 4 most wells fail to supply enough water for domestic use from depths of less than 300 feet, probably because they penetrate thick sections of unfractured shale or well-cemented sandstone. In area 5 the yield of wells is unpredictable, commonly because of faulting. The water in the shallow bedrock aquifers of the region is mostly of the sodium bicarbonate or the calcium bicarbonate type. Saline water has been encountered at depths as shallow as 100 feet, but fresh water has been obtained at depths approaching 1,000 feet. Water from the bedrock is soft to moderately hard, but it may contain undesirable amounts of iron. Most water from the alluvium is of the calcium bicarbonate type and is generally harder and contains more iron than water from the bedrock.