Which philosophy meant that the united states was meant to extend its boundaries all the way to the pacific?

Manifest destiny
   This phrase was coined in 1845. It articulated the idea that justified and defined  U.S. territorial expansion in the 19th century. Manifest Destiny posited that the United States of America was destined, by the almighty God, to expand her dominion and the spread of democracy as well as capitalism across the entire North American continent.

They were constantly being overlooked as a people and were being controlled by people who weren't really native to their homeland.