Grizzly Bear Ursus arctos The grizzly bear was first mentioned by the expedition about 25 miles below the mouth of the Niobrara River, along the Nebraska-South Dakota boundary, where a "White Bear Clift" was named as the site where a grizzly bear had once been killed. Bear tracks were seen on October 7, 1804, on Fox Island, near the mouth of the Moreau River in South Dakota. However, the first actual encounter with a grizzly was on October 20, 1804,when one was wounded near t

The expedition left the common boundary of Nebraska and South Dakota on September 8, 1804. Moving north in South Dakota, large herds of bison were seen, as well as elk and deer. They passed the mouth of the White River on September 15, soon encountering "multitudes" of prairie dogs and vast herds of bison and antelope. By September 20 they had reached the Big Bend of the Missouri River, sending two men by horseback across the narrow peninsula to hunt and await their arrival a