How did the united states acquire new territory and expand trading in the pacific

The united states acquired land, it was just by sheer exploration and new colonizing of land. They explored rives and different natural resources like wood and grain, and started to make new towns around the places they visited that didn't start as towns, they started as just places that would help upkeep of the thing they were monopolizing. Eventually people started population those cities and they began to monopolize all of the resources that the land had to offer. With no competition for resource people began to need what they had to offer and trade came to them with ease.