Benfey was born in Merion, Pennsylvania but spent most of his childhood in Richmond, Indiana and attended The Putney School. He began his undergraduate studies at Earlham College, where his father was a professor in the Chemistry department, and completed his B.A. at Guilford College. Benfey holds a Ph.D. from Harvard University.

Benfey is a specialist in 19th and 20th century American literature. He is also an established essayist and critic who has been published in The New York Times Sunday Book Review, The New Republic, The New York Review of Books, and The Times Literary Supplement.