Leer previously served as the president and chief executive officer of Arch Coal, Inc. since the company was formed in July 1997 until April 2006. Prior to the formation of Arch Coal, Leer served as president and chief executive officer of Arch Mineral Corporation, one of Arch Coal's predecessor companies. Leer also has held executive management positions with The Valvoline Company (a subsidiary of Ashland Inc.), Ashland Inc. and Ashland Coal, Inc.

A native of Vermillion, South Dakota, Leer graduated from the University of the Pacific with a B.S. in electrical engineering in 1975. He received his MBA from Washington University's Olin School of Business in 1977. The University of the Pacific awarded him an honorary doctorate in May 1993. Leer serves as a Board of Regent with the University of the Pacific as well as a Board of Trustee for Washington University.

In addition to his executive and board responsibilities with Arch Coal, Leer serves on the boards of Norfolk Southern Corporation, USG Corporation, and the Western Business Roundtable. He is past chairman of the Coal Industry Advisory Board of the International Energy Agency in Paris. He also is a member of The Business Roundtable and the National Association of Manufacturers. Leer is chairman of the American Coalition for Clean Coal Electricity, also serving on the Boards of the National Coal Council and the National Mining Association. He is an Executive Board Member of the Greater St. Louis Area Boy Scouts of America.

Leer is married to the formerly Beverly Uhl. They reside with their son, in suburban St. Louis County, Missouri.