After the industrial revolution, people wanted to expand westward to the west coast. they believed it was their destiny to expand all the way to the west coast even before it was America's land.
"the only thing to fear is fear itself".
John F. Kennedy
"After the Great Depression and after public urging, a nationwide public competition was held to determine a design for a memorial that would honor President Thomas Jefferson's bold vision for westward expansion for America."
President Polk's campaign slogan was "54' 40" or Fight!". This encouraged Americans to go out west an elect him president.
"Now, of course, the great thing about the solar system as a frontier is that there are no Indians, so you can have all the glory of the myth of the American westward expansion without any of the guilt."
In 1840, there was a gold rush in California and everyone packed up everything they owned and rushed to California along the Oregon Trail.
With many skirmishes and battles, we were able to double the size of America by taking half of mexico and letting our citizens live there, as it was getting crowded on the east coast.