Question

How did the United States manage to expand its territory across the continent

Answer 1

Manifestation, or manifest destiny. The expansion of a country.

Answer 2

So, the United States wanted to find more opportunity in different places than where they were currently at. Of course they would go and expand their territory. United States pretty much bought out their way across the continent, with New Orleans and West Florida for $10 million as an example. They possibly fought for a bit of it, but most of it was bought out. :)

-Mabel <3