Semi-bituminous coals are found on the eastern edge of the great Appalachian Field. Starting with Tioga and Bradford Counties of northern Pennsylvania, the bed runs southwest through Lycoming, Clearfield, Centre, Huntingdon, Cambria, Somerset and Fulton Counties, Pennsylvania; Allegheny County, Maryland; Buchannan, Dickinson, Lee, Russell, Scott, Tazewell and Wise Counties, Virginia; Mercer, McDowell, Fayette, Raleigh and Mineral Counties, West Virginia; and ending in northeastern Tennessee, where a small amount of semi-bituminous is mined.
The largest of the bituminous fields is the Appalachian. Beginning near the northern boundary of Pennsylvania, in the western portion of the State, it extends southwestward through West Virginia, touching Maryland and Virginia on their western borders, passing through southeastern Ohio, eastern Kentucky and central Tennessee, and ending in western Alabama, 900 miles from its northern extremity.
The next bituminous coal producing region to the west is the Northern Field, in north central Michigan. Still further to the west, and second in importance to the [Pg 169] Appalachian Field, is the Eastern Interior Field. This covers, with the exception of the upper northern portion, nearly the entire State of Illinois, southwest Indiana and the western portion of Kentucky.
The Western Field extends through central and southern Iowa, western Missouri, southwestern Kansas, eastern Oklahoma and the west central portion of Arkansas. The Southwestern Field is confined entirely to the north central portion of Texas, in which State there are also two small isolated fields along the Rio Grande River.
The remaining bituminous fields are scattered through what may be termed the Rocky Mountain Region, extending from Montana to New Orleans. A partial list of these fields and their location follows:
| Judith Basin | Central Montana | |
| Bull Mountain Field | Central Montana | |
| Yellowstone Region | Southwestern Montana | |
| Big Horn Basin Region | Southern Montana | |
| Big Horn Basin Region | Northern Wyoming | |
| Black Hills Region | Northeastern Wyoming | |
| Hanna Field | Southern Wyoming | |
| Green River Region | Southwestern Wyoming | |
| Yampa Field | Northwestern Colorado | |
| North Park Field | Northern Colorado | |
| Denver Region | North Central Colorado | |
| Uinta Region | Western Colorado | |
| Uinta Region | Eastern Utah | |
| Southwestern Region | Southwestern Utah | |
| Raton Mountain Region | Southern Colorado | |
| Raton Mountain Region | Northern New Mexico | |
| San Juan River Region | Northwestern New Mexico | |
| Capitan Field | Southern New Mexico |
Along the Pacific Coast a few small fields are scattered in western California, southwestern Oregon, western and northwestern Washington.
Most of the coals in the above fields are on the border line between bituminous and lignite. They are really a low grade of bituminous coal and are known as sub-bituminous or black lignites.
Lignites—These resemble the brown coals of Europe and are found in the western states, Wyoming, New Mexico, Arizona, Utah, Montana, North Dakota, Nevada, California, Oregon and Washington. Many of the fields given as those containing bituminous coals in the western states also contain true lignite. Lignite is also found in the eastern part of Texas and in Oklahoma.
Alaska Coals—Coal has been found in Alaska and undoubtedly is of great value, though the extent and character of the fields have probably been exaggerated. Great quantities of lignite are known to exist, and in quality the coal ranges in character from lignite to anthracite. There are at present, however, only two fields of high-grade coals known, these being the Bering River Field, near Controllers Bay, and the Matanuska Field, at the head of Cooks Inlet. Both of these fields are known to contain both anthracite and high-grade bituminous coals, though as yet they cannot be said to have been opened up.