Answer:
The Trappers wanted to find a new source of animal fur for selling.
Step-by-step explanation:
The exhaustion and extinction of animals in the Eastern regions led many trappers to move west and find new sources of animal fur. The fur trade almost came to a full stop before the expansion, because the competition and the efficiency of trappers and hunters put enormous pressure on the animal's numbers. The expansion west revitalized the trade but took the consequences to new lands, causing the disappearance or near extinction of other species.