He was an explorer of the watershed of the Upper Missouri River in present day North Dakota, South Dakota and Montana. Glass was famed, most of all, as a frontier folk hero for his legendary cross-country trek after being mauled by a grizzly bear.
General Ashley's Expedition
Glass' most famous adventure began in 1822, when he responded to an advertisement in the Missouri Gazette and Public Adviser, placed by General William Ashley, which called for a corps of 100 men to "ascend the river Missouri" as part of a fur trading venture. These men would later be known as Ashley's Hundred.
Besides Glass, others who joined the enterprise included notables such as Jim Beckwourth, Thomas Fitzpatrick (trapper), David Jackson, John Fitzgerald, William Sublette, Jim Bridger, and Jedediah Smith.
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.
Near the forks of the Grand River in present-day Perkins County, in August 1823, while scouting ahead of his trading partners for game for the expedition's larder, Glass surprised a grizzly bear mother with her two cubs. Before he could fire his rifle, the bear charged, picked him up, and threw him to the ground. The bear threw his flesh to its cubs. Glass got up, grappled for his knife, and fought back, stabbing the animal repeatedly as the grizzly raked him time and again with her claws.
Glass managed to kill the bear with help from his trapping partners, Fitzgerald and Bridger, but was left badly mauled and unconscious. Henry (who was also with them) 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 19 years old) and Fitzgerald (then 23 years old) 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 incorrectly reported to Henry that Glass had died.
The Odyssey to Fort Kiowa
Despite his injuries, Glass regained consciousness. He did so only to find himself abandoned, without weapons or equipment, suffering from a broken leg, the cuts on his back exposing bare ribs, and all his wounds festering. Glass lay mutilated and alone, more than 200 miles (320 km) from the nearest American settlement at Fort Kiowa on the Missouri.
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.
Deciding that following the Grand River would be too dangerous because of hostile Indians, Glass crawled overland south toward the Cheyenne River. It took him six weeks to reach it.
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 as well as providing him with food and a couple of weapons to defend himself, 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, he 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 killed. 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.
Glass would again return to the frontier as a trapper and fur trader. Later he was employed as a hunter for the garrison at Fort Union. He was killed with two fellow trappers in the winter of 1833 on the Yellowstone River in an attack by the Arikara.
According to the book The Deaths of the Bravos by John Myers Myers, the Arikara in April 1833 later tried to pass themselves 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 Fitzgerald and Bridger left him for dead in 1823. Alarmed by this, Gardner surmised that the Indians were actually the Arikaras. The Indians were seized and executed in response to the death of Hugh Glass.
- Western writer Frederick Manfred wrote Lord Grizzly, an account of Glass' ordeal.
- Richard Harris played in Man in the Wilderness (1971), an historical movie based upon Hugh Glass story.
- Roger Zelazny and Gerald Hausman meshed the stories of John Colter and Hugh Glass in the 1994 novel Wilderness.
- The song Six Weeks by Of Monsters and Men is "[...]inspired by the true tale of American frontiersman Hugh Glass, seemingly left for dead after 86ing a bear that attacked him." 
- Leonardo DiCaprio will play Glass in the film The Revenant directed by Alejandro González Iñárritu.
- Jon T. Coleman. Here Lies Hugh Glass: A Mountain Man, a Bear, and the Rise of the American Nation 2013
- Dale L. Morgan. Jedediah Smith and the Opening of the American West (1952)
- "Hugh Glass", Bruce Bradley (1999) ISBN 0-9669005-0-2
- "Lord Grizzly", Fredrick Manfred (1954) ISBN 0-8032-8118-8
- "Saga of Hugh Glass: Pirate, Pawnee and Mountain Man", John Myers Myers (1976) ISBN 0-8032-5834-8
- "Hugh Glass, Mountain Man", Robert M. McClung (1990) ISBN 0-688-08092-8
- "The Song of Hugh Glass" (part of "A Cycle of the West"), John G. Neihardt (1915)
- Hilmarsdóttir, Nanna Bryndís. "Of Monsters and Men Biography". Of Monsters and Men. 2011