The Call of the Wild is a novel by American writer Jack London. The plot concerns a previously domesticated happy dog named Buck, whose primordial instincts return after a series of events leads to his serving as a sled dog in the Yukon during the 19th-century Klondike Gold Rush, in which sled dogs were bought at generous prices. Published in 1903, The Call of the Wild is London's most-read book, and it is generally considered his best, the masterpiece of his so-called "early period". Because the protagonist is a dog, it is sometimes classified as a juvenile novel, suitable for children, but it is dark in tone and contains numerous scenes of cruelty and violence. London followed the book in 1906 with White Fang, a companion novel with many similar plot elements and themes as Call of the Wild, although following a mirror image plot in which a wild wolf becomes civilized by a mining expert from San Francisco named Weedon Scott.