The story of John Wesley Powell is a classic: A one-armed Civil War veteran, with scant assistance from the U.S. government, organizes a motley crew to chart the "Great Unknown" of the Green and Colorado Rivers. Next year marks the sesquicentennial of the 1869 Powell expedition, and publishers are releasing a raft of books revisiting the adventure. 

The Powell Expedition: New Discoveries About John Wesley Powell's 1869 River Journey (University of Nevada Press, 2017), by Don Lago, is for those who already know the Powell story and are eager for six chapters about the mystery of James White—who may (or may not) have floated the river before Powell—or nearly 100 pages pondering the fate of the three men who left the expedition just days before its conclusion and were never seen again. 

River Master: John Wesley Powell's Legendary Exploration of the Colorado River and Grand Canyon (Countryman Press, 2017) is, unfortunately, overwritten and underwhelming; author Cecil Kuhne has never met an adverb he didn't like. 

By far the best of the bunch is John F. Ross's The Promise of the Grand Canyon: John Wesley Powell's Perilous Journey and His Vision for the American West (Viking, 2018). This biography is, to borrow one of Ross's descriptions of Powell, "clear, authoritative, and dramatic." Ross covers Powell's upbringing in a staunch abolitionist home and recounts the Grand Canyon exploration with cinematic flair. He then dives into Powell's subsequent career as head of the U.S. Geological Survey, during which Powell warned about the fragility of the arid West. Ross's portrait of this complicated figure reveals how "generations of dueling developers and environmentalists have claimed [Powell] as their guiding star." 

This article appeared in the July/August 2018 edition with the headline "Back Into the 'Great Unknown.'"