It was the largest bear they'd ever seen, a great grizzly bear that weighed an estimated 600 pounds. A "most tremendous looking animal, and extreemly hard to kill," wrote Lewis in his journal on May 5, 1805. Clark described the grizzly as "verry large and a turrible looking animal." Clark and another member of the expedition fired 10 shots at it before it died.

Several tribes of Native Americans had told Lewis and Clark about grizzly bears. The tribes would only attack these great bears if there were 6-10 people in their hunting party, and even then the bears would sometimes kill one of them. The first grizzlies Lewis saw during the expedition were two smaller bears. He and another hunter had easily killed one of them. That day Lewis wrote in his journal that although the Native Americans with their bows and arrows might have problems, the grizzlies were no match for skilled rifleman. He soon changed his mind.