Final answer:
The area of the United States that was just forming around 1803 was the West through the Louisiana Purchase.
Step-by-step explanation:
The area of the United States that was just forming around 1803 was the West. In that year, the United States acquired the Louisiana Territory from France through the Louisiana Purchase. This vast region extended from the Mississippi River to the Rocky Mountains and covered what is now known as the Great Plains and the western part of the United States.
Learn more about Formation of the United States in the early 1800s