Lost in the Yellowstone: Truman Everts's "Thirty-Seven Days of Peril" The incredible true adventure of the only person known to have survived so long while lost in Yellowstone wilderness. When Truman Evert visited the Yellowstone area in 1870, the Yellowstone belonged to myth. Scattered reports of a mostly unexplored wilderness filled with natural wonders caught the public's--and Evert's--attention. Although fifty-four, nearsighted, and an inexperienced woodsman, he joined the expedition determined to map and investigate the mysterious Yellowstone. Separated from his party, and then abandoned by his horse, Evert embarked on one of the most grueling survival adventures recorded on the American frontier.