Mark Klett (b. 1952) is a photographer whose work explores relationships among landscape, history, human intervention and the passage of time. Born in Albany, New York, Klett earned a B.S. in geology from St. Lawrence University in 1974 and worked for the U.S. Geological Survey before earning an M.F.A. in photography from the State University of New York at Buffalo in 1977. That year, he helped establish the Rephotographic Survey Project, which located sites photographed during 19th century surveys of the American West and created new photographs from the same vantage points. By pairing historical and contemporary images, the project revealed changes caused by urban development, mining, water management and other human interventions while also examining how photographers shape perceptions of landscape. Klett has worked collaboratively with photographer Byron Wolfe on projects that combine historic and contemporary photographs, maps, field research and digital imaging to reveal how landscapes—and perceptions of them—change over time. Their Yosemite in Time project re-examined iconic views by photographers including Carleton Watkins, Eadweard Muybridge and Ansel Adams, while later projects investigated the Grand Canyon and Glen Canyon. Klett taught at Arizona State University for 40 years, where he is Regents’ Professor Emeritus.