What city grew to over 4,000 people by 1840 and marked america’s move west?

The first person to reach the area to what is known nowadays as Kansas City, Missouri was French explorer Etienne de Veniard. After a series of shifts in the control of the territory, which included a brief of control by Spain (Treaty of Paris in 1763), it ultimately became United States territory after the Lousiana Purchase in 1804.

During that time, the city was known as The town of Kansas had become a critical point in the expansion to the west, as settlers stopped there in order to get supplies and shelter. Due to this key position, numerous businesses started opening that attracted people to come and live in the area.