Grizzly Bear and human travels:
Regarding Grizzly Bears and humans, though, they both reached Alaska about the same time, 15,000 years ago. And in the next 15,000 years, humans completely populated North and South America, while bears only expanded as far south as Central Mexico and as far east as Kansas but not reaching the Mississippi. This indicates that humans have a much greater dispersal ability than Grizzly Bears.
So as both these species dispersed, Grizzly Bears were tolerated and respected and even revered by Native Americans, wherever they came in contact. However, this symbiosis came to an abrupt end, however, when the first Europeans invaded from Europe, bringing firearms. By 1750, the Europeans had reached into much of occupied Grizzly Bear habitat.
The early settlers killed Grizzlies whenever they encountered them. But by 1850, they still occupied almost all of their former range but in greatly reduced numbers. California alone was estimated to support about 10,000 Grizzly Bears. The last one was killed around 1920. They estimate that there were about 50,000 Grizzly Bears in the contiguous United States at the height of their dispersal. Now there are about 1,000.