If you really want to get all huffy about borders, take a look at what Jefferson did:
In 1803 Napoleon decided to consolidate his resources for a new round of the conflict with England by selling the vast Louisiana region, which stretched from the Mississippi Valley to the Rocky Mountains. Although the asking price, $15 million, was a stupendous bargain, assuming the cost meant substantially increasing the national debt.
More significantly, what became known as the Louisiana Purchase violated Jefferson's constitutional scruples. Indeed, many historians regard it as the boldest executive action in American history. But Jefferson never wavered, reasoning that the opportunity to double the national domain was too good to miss. The American West always triggered Jefferson's most visionary energies, seeing it, as he did, as America's future, the place where the simple republican principles could be constantly renewed.
In one fell swoop he removed the threat of a major European power from America's borders and extended the life span of the uncluttered agrarian values he so cherished. Even before news that the purchase was approved reached the United States in July 1803, Jefferson dispatched his private secretary, Meriwether Lewis, to lead an expedition to explore the new acquisition and the lands beyond, all the way to the Pacific.
It ain't all about guns and fences.