The naturalist and explorer Alexander von Humboldt (1769–1859) achieved unparalleled fame in his own time. Today, his enormous legacy to American thought is virtually unknown. In The Humboldt Current, Aaron Sachs seeks to reverse this obscurity by tracing Humboldt’s pervasive influence on American history, specifically looking at the lives and careers of four explorers: J. N. Reynolds, the founder of the 1838–1842 U.S. Exploring Expedition; Clarence King, the first director of the U.S. Geological Survey; George Wallace Melville, chief engineer on the disastrous 1879 Jeannette expedition to the North Pole; and John Muir, founder of the Sierra Club. In Sachs’s view, all four of these men were alienated Romantics who used Humboldt’s notion of "unity in diversity" as a way of critiquing their increasingly industrialized society. Moreover, as Sachs argues, their examples laid the groundwork for an ecological tradition even more radical than the one that has come down to us today. Sachs’s treatment of Humboldt’s legacy also includes discussions of the writers and artists most in his debt: Emerson, Whitman, Thoreau, Melville, Poe, and Frederic Church. Reminiscent of Louis Menand’s bestselling The Metaphysical Club, The Humboldt Current is a colorful, superbly written and carefully researched work that offers a fundamental reinterpretation of nineteenth century American history.