American settlement seemed to be unstoppable. By 1840, settlers had occupied all of the land 
east of the Mississippi River and had organized most of the area into states. This rapid 
expansion was caused by the market revolution and the extraordinary expansion of 
transportation and commerce that accompanied the market revolution. The speed and success 
of the expansion was a source of great pride for Americans and encouraged further 
settlement. By 1848, the United States had become a continental nation. 
a. The Fur Trade 
From the 1670s to the 1840s, the fur trade was an important spur to North American 
exploration. In 1824, William Henry Ashley instituted the rendezvous system, a yearly 
trade fair (modeled on traditional Indian trade gatherings) to which trappers brought their 
catch of furs. The event was a many-day affair characterized by trading, drinking, and 
gambling, bringing together many nationalities and people of mixed race in a short-lived 
community. By the 1840s the population of beaver in the West was virtually destroyed 
and settlement would replace frontier trade.