The answer is the canon of medicine!
A) fishermen , trappers and traders
The worry they would run into an enemy or something dangerous. They could also not carry a lot so they could run out of supplies.
The phrase, coined by a newspaper writer in the 1840s, implied that it was the obvious path of the United States to expand its territory as far westward as possible—the right and appropriate fate of the country. ... The map represents the old Manifest Destiny.
California, Nevada, Arizona, Utah, Texas, Colorado, New Mexico, Wyoming, Kansas, and Oklahoma.
