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Wyoming Coal

Wyoming has been the top coal-producing state in the United States since 1986; in fact, the coal extracted from Wyoming’s coal mines accounts for more than 40 percent of the annual U.S. coal supply. The production of coal in Wyoming contributes hundreds of millions of dollars in revenue to state and local governments annually. The majority of coal produced in Wyoming is used for electricity generation, but some is also sent to industrial sites, where it is used for things like heating bentonite kilns, producing cement and steel, and trona processing. See the WSGS pages on Coal Production & Mining for more information on coal mining in Wyoming.

Wyoming is divided into two major coal regions: the Rocky Mountain and Northern Great Plains provinces. These areas are further subdivided into 10 coal fields, defined by the extent of coal-bearing formations within sedimentary basins (see map at right).

Coal in Wyoming occurs in rock sequences deposited during the Cretaceous Period 138–65 million years ago (mya), the Paleocene Epoch (65–55 mya), and the Eocene Epoch (55–43 mya). The climate at those times was mostly warm and humid, suitable for substantial growth of vegetation in brackish and freshwater swamps. Organic material that accumulated in these environments was buried and transformed into the coal found across Wyoming today. See the Coal Geology page for more information.

Wyoming Coal Mining

Commercial mining of Wyoming coal began in the mid-1860s with the arrival of the Union Pacific Railroad. Since 1865, more than 12.5 billion short tons of coal have been mined in Wyoming.

In 2021, 239 million short tons (MT) of coal were produced in Wyoming, up 9 percent from the 218 MT produced during 2020. Coal was produced from mines in Campbell, Sweetwater, and Lincoln counties in Wyoming. More details can be found on the WSGS Coal Production & Mining page.

Coal produced in Wyoming is generally subbituminous and moderately low ash. Some coal deposits in the Powder River Basin (PRB) are considered “super compliant” by environmental requirements, with less than 0.2 percent sulfur. This makes Wyoming coal an excellent “steam coal,” which is highly desirable for electricity generation across the United States. More than 90 percent of the coal produced in the United States is consumed for electricity generation.

Coal mined from the PRB is consistently the cheapest coal to extract from the ground due to the coal occurring in thick (45+ foot) seams that are near the surface and easily strip mined using large machinery. This combination of factors also makes PRB coal mines the most productive in the nation, with the highest volumes mined per employee per hour.

Wyoming Coal Research

The WSGS has a long tradition of coal research. The coal fields and coal-bearing strata of Wyoming have been mapped and correlated in detail. The WSGS has published more than 40 coal publications over the past 50 years and serves as a repository for coal information and resources, which includes a collection of historic mine maps.

The WSGS Energy and Minerals team studies coal resources to determine the extent of known coal beds and coal quality. The team also interprets the history of coal deposition and evolution of the sedimentary basins where coal formed. Stratigraphic and coal quality data compiled from WSGS studies can be used for exploration in the coal and petroleum industries, for developing government regulations, and for scientific investigations.

Publications about coal in Wyoming can be searched for in the WSGS Publication Search and WSGS Publications Sales and Free Downloads websites.