As of 2020, I’m Professor of History at the University of Pennsylvania. Previously, I taught at Stony Brook University. I study the overlapping historical dimensions of landscape, environment, technology, science, religion, culture, and law. I have regional expertise in the American West. My last book was Trees in Paradise: A California History.

I earned my degrees from Utah State University, the University of Montana, and Stanford. I have received fellowships and grants from institutions such as the American Council of Learned Societies, the National Humanities Center, the National Endowment for the Humanities, and the Alfred P. Sloan Foundation. See my curriculum vitae.

My book On Zion’s Mount won the Francis Parkman Prize from the Society of American Historians for the best-written non-fiction book on an American theme, a literary award that honors the “union of the historian and the artist.” In 2014, the Dallas Institute presented me the Hiett Prize in the Humanities; in 2017, the Carnegie Corporation of New York named me an Andrew Carnegie Fellow; and in 2018, the American Academy in Berlin awarded me a Berlin Prize. My current project (under contract with Basic Books) is provisionally titled Survival of the Oldest: Ancient Trees in Modern Times.