Hey there helpful people ☻ This is a DBQ question for APUSH, and I need both primary documents as well as an argument...any help whatsoever would be greatly appreciated. ☺
When the Monroe Doctrine was first promulgated in 1823, Europe was still recovering from the Napoleonic Wars earlier in the century. One of the effects of that war was that colonies in the New World began to break away from their Mother Countries, since they had been severely weakened during the Wars. Notably, Spain, which had claims and colonies encompassing most of South America, had been losing her colonies at a rapid pace during the early half of the 1800's.
The Monroe Doctrine (actually, President Monroe's "State of the Union" address for that year) in addition to promoting isolationism and non entangling alliances, suggested rather than warned the Old World regarding the expansion of old or the establishment of new colonies in the New World. Europe may have appeared to acquiesce, but only because of her weakened condition, since the young United States could not really defend the Western Hemisphere then.
By the latter part of the 1800's, however, the United States could! The Spanish-American War in 1898 finally got Spain out of Cuba, among other things, and began to expand its political influence throughout Latin America. With a technically advanced and growing Navy the US could make good its threats. During the British-German blockade of Venezuela in 1903, the principles in the Doctrine were reaffirmed, and both nations were warned not to interfere in the Caribbean.
So are you supposed to be writing your own DBQ and providing the documents? Is that what you're saying? Tough one. Contact me if that's what you need, I'll think about it.
As far as the question goes, leaving the documents aside, it became the cornerstone of US foreign policy because it was a fairly obvious statement of the US's interests (or what would become its interests as it became more powerful). Any major power will want to have a "neighborhood" that it dominates. Dominating the Western Hemisphere would add greatly to US security and prosperity.
As far as how it happened, the main things you could talk about would be wars:
- The Mexican-American war because it enlarged the US so much and added to its strategic position (giving it a truly continental scope)
- Same for getting the Oregon Territory from GB (not a war, of course).
- The Civil War -- cemented the unity of the US, and its end allowed the US to help eject the French from Mexico.
- Spanish American War -- extended the reach of the US in the Caribbean.
So, overall I'd be saying that the "why" is because it was clearly in the US's interests. I'd say the "how" is centered on the US becoming stronger -- strong enough to enforce its claims.
It became a justification for our foreign policy because it was convenient. 75 years later we could claim that it was always an American policy, a tradition, and therefore a continuation of that policy later of course had to be justifiable. It's part of a larger pattern of similar actions in imperial history. We "claimed" the Pacific Northwest because a party of explorers had walked through it in the early 1800s for a completely different reason.