St. Louis, MO - October 8, 1998 - Arch Coal, Inc. (NYSE:ACI) today announced that its Black Thunder Mine in Campbell County, Wyo., had recently shipped its 500 millionth ton of coal, a milestone never before achieved by a single U.S. coal mine.

"Through a total commitment to safety, efficiency and continuous improvement, the employees of Thunder Basin Coal Company have made Black Thunder the most productive coal mine in U.S. history," said Steven F. Leer, president and chief executive officer of Arch Coal. "They should be extremely proud of this remarkable feat."

The Black Thunder Mine is one of the largest coal mines in North America, with projected production of 45 million tons in 1998. (That total is the fuel equivalent of roughly 135 million barrels of imported oil.) The mine has a proven and probable reserve base of well over 1.1 billion tons.

"The low-sulfur coal produced by Black Thunder is a vital energy source," Leer said. "This year, Black Thunder will provide the clean-burning fuel for more than 2.5% of the electricity generated in the United States. In this way, Black Thunder makes a very significant contribution to both the U.S. economy and our modern way of life."

Arch Coal is the nation's second largest coal producer, with subsidiary operations in West Virginia, Kentucky, Virginia, Illinois, Wyoming, Colorado and Utah. Coal is the fuel source for 57% of the electricity generated in the United States.