David Wayne Countryman was born on May 21, 1943 in Ottumwa, Iowa. He received his B.S. (1966) and M.S. (1968) in forest management from Iowa State University and his Ph.D. (1973) in forest management and planning from the University of Michigan. Before teaching at Iowa State, Countryman worked for the U.S. Forest Service (1968-1974) as a Forester and Assistant Ranger. He joined Iowa State University as an Associate Professor (1975-1980) in the Department of Forestry and was promoted to Professor (1980-2000). He was named Professor Emeritus (2001) of Forestry.

During his tenure at Iowa State, Countryman developed and taught the capstone course in the Department of Forestry. He also taught several other courses, primarily in forest management, and conducted research on the economic potential of Iowa's woodlands and the effective development and management of forests and recreation resources in the Midwest. Countryman retired in 2000.

Countryman was a member of numerous professional associations and academic societies including: Gamma Sigma Delta, Xi Sigma Pi, Midwest Forest Economists, Association for Temperate Agro-Forestry, Society of American Foresters, Iowa Society of American Foresters, American Association for the Advancement of Science, Sigma Xi, Iowa Tree Farm Committee, and Iowa Department of Natural Resources Forest Stewardship Committee. Countryman also received several awards including the Webster County (Iowa) Soil Conservation Award (1986) from the Izaak Walton League of America (Fort Dodge Chapter), the Soil Conservation Award (1987), and a Certificate of Appreciation from the American Forest Council (1992).

Countryman married Roberta Rae, and they had two children: William Bruce and Michelle Rae.