Little is known about Glass's early life. He was probably born in Pennsylvania. Stories about Glass assert that he was a sailor, a reluctant pirate with Jean Lafitte, and an honorary Pawnee. Best documented, however, are his actions as an explorer of the watershed of the Upper Missouri River in present day South Dakota and Montana, Glass was famed most of all for his legendary cross-country trek after being mauled by a grizzly bear. A 1971 movie entitled Man in the Wilderness, starring Richard Harris and John Huston, was loosely based on this story.
Early in the trek, Glass established himself as a hard-working fur trapper. He was apparently wounded on this trip in a battle with Arikaras, and later traveled with a party of 13 men to relieve traders at Fort Henry at the mouth of the Yellowstone River. The expedition, led by Andrew Henry, planned to proceed from the Missouri, up the valley of the Grand River in present-day South Dakota, then across to the valley of the Yellowstone.
Glass managed to kill the bear with help from his trapping partners, Fitzgerald and Bridger, but was left badly mauled and unable to walk. When Glass lost consciousness, Henry became convinced the man would not survive his injuries.
Henry asked for two volunteers to stay with Glass until he died, and then bury him. Bridger (then 17 years old) and Fitzgerald stepped forward, and as the rest of the party moved on, began digging his grave. Later claiming that they were interrupted in the task by an attack by "Arikaree" Indians, the pair grabbed Glass's rifle, knife, and other equipment, and took flight.
Bridger and Fitzgerald reported to Henry -- wrongly it turned out -- that Glass had died.
In one of the more remarkable treks known to history, Glass set his own leg, wrapped himself in the bear hide his companions had placed over him as a shroud, and began crawling. To prevent gangrene, Glass laid his wounded back on a rotting log and let the maggots eat the dead flesh.
Glass survived mostly on wild berries and roots. On one occasion he was able to drive two wolves from a downed bison calf, and feast on the meat. Reaching the Cheyenne, he fashioned a crude raft and floated down the river, navigating using the prominent Thunder Butte landmark. Aided by "friendly" natives who sewed a bear hide to his back to cover the exposed wounds, Glass eventually reached the safety of Fort Kiowa.
After a long recuperation, Glass set out to track down and avenge himself against Bridger and Fitzgerald. When he found Bridger, on the Yellowstone near the mouth of the Bighorn River, Glass spared him, purportedly because of Bridger's youth. When he found Fitzgerald, and discovered that Fitzgerald had joined the United States Army, Glass purportedly restrained himself because the consequence of killing a U.S. soldier was death. However, he did recover his lost rifle.
Glass, along with 4 others, was dispatched by Ashley to find a new trapping route, by going up the Powder River, then across and down the Platte to the bluffs. The party set off in a bullboat. Near the junction with the Laramie River, they discovered some 38 Indian lodges, with several Indians on the shore. The Indians appeared to be friendly, and the trappers initially believed them to be Pawnees. After going ashore and dining with the Indians, Glass discovered that the Indians actually belonged to the Arikara nation, who, after several past encounters, were anything but friendly with the whites. The party quickly got in the bull boat and paddled for the far shore. The Indians promptly swam in after them and both reached the shore around the same time. Two men, Marsh and Dutton, escaped and reunited later, but the other two, More and Chapman, were quickly overtaken and slaughtered. Glass was lucky enough to find a group of rocks to hide behind, and was not discovered by the Arikaras. Glass also found his knife and flint in his shot pouch after the ordeal. He fell in with a party of Sioux and travelled with them back to Fort Kiowa.
Glass' survival odyssey has been recounted in numerous books. A monument to Glass now stands near the site of his mauling on the southern shore of Shadehill Reservoir on the forks of the Grand River.
According to the book "The Deaths of the Bravos" by John Myers Myers, the Arikara in April of 1833 later tried to pass off as friendly Minitaris Indians to a party of trappers employed by Amfurco. However, Johnson Gardner one of the trappers recognized a rifle that one of the Indians had as the very rifle Glass got back from Fitzgerald after his epic journey for revenge after Fitzgerald and Bridger left him for dead in 1823. Alarmed by this, Gardner correctly surmised that the Indians were actually Arikara's. The Indians were seized and their execution avenged the death of Hugh Glass.