Samuel Pfrimmer Hays was a pioneering environmental, social, and political historian of the United States. Born in Corydon, Indiana, and raised on a local dairy farm, he earned a graduate degree from Swarthmore College in 1948 and a Ph.D. at Harvard University under Professor Frederick Merk.

He authored multiple influential works, including:

• The Response to Industrialism 1885-1914 (1957)
• Conservation and the Gospel of Efficiency (1959)
• American Political History as Social Analysis (1980)
• Beauty, Health, and Permanence: Environmental Politics in the United States, 1955-1985 (1989)
• A History of Environmental Politics since 1945 (2000)
• Wars in the Woods: The Rise of Ecological Forestry in America (2006)
• The American People and the National Forests: The First Century of the U.S. Forest Service (2009)

He established the Archives of Industrial Society at The University of Pittsburgh, where he served as a professor of history from 1960 until 1990. Hays served as president of the Urban History Association in 1992. He was the first recipient of the American Society for Environmental History Distinguished Scholar award in 1997 and received the Distinguished Service Award from the Organization of American Historians in 1999.

An environmental activist, Hays owned a 311-acre tract of land in Harrison County, Indiana, near Corydon, which he donated to the county as a nature preserve, now known as the Hayswood Nature Reserve.