Muir considered Alaska his living glacier laboratory where he could imagine glacial behavior in the Sierra during the Ice Age over 10,000 years earlier. He traveled to Alaska 7 times in 21 years. His last trip was with naturalist John Burroughs (left) and over 25 scientists and artists on the Harriman expedition in 1899 to thoroughly study and document the coasts of Alaska. (Muir and Burroughs)