Monroe's Mantra

The Monroe Doctrine has been insanely, profoundly influential in American history. When it was first presented, it was generally received favorably, not just in the U.S. but also in Latin America and even Britain. (Source)

America was taking a stand against European countries trying to take over areas that had just fought for independence—what's bad about that? Plus, by doing so they were protecting new British trading interests. Everybody wins. Except maybe Spain.

Of course, at the time the U.S. didn't really have the power to back up their claims, which was okay because European nations weren't actually planning to re-take Latin America anyway. Some people, especially in European countries, thought the statement a bit presumptuous. Who did those Americans think they were, anyway? (Source)

The 19th Century: the Doctrine Snowballs

The idea of the Monroe Doctrine stuck and became more powerful throughout the 19th century. It quickly became tied up with the ideology of Manifest Destiny. Basically the idea was that the U.S. was now the guardian of the western hemisphere, and therefore had a sort of divine right to expand and extend their influence over the west. You know, to protect it from colonial powers. It makes sense if you're trying to take over western land. (Source)

James K. Polk reaffirmed the Monroe Doctrine in his first address to Congress, and continued to use its ideas when dealing with the annexation of Texas.

It really became known as "the Monroe Doctrine" in the 1850s, and even more firmly during the Emperor Maximilian incident in Mexico. In 1864, Napoleon III installed Emperor Maximilian on the throne of Mexico—which already had a president. It didn't go well, and the U.S. helped Mexico revolt against the French interference. Maximilian met a grim fate in 1867. (Source)

The Monroe Doctrine was also brought up during various conflicts between Spain and Cuba in the 1800s. It was explicitly used in 1895, when President Grover Cleveland forced Britain to agree to mediation about a border dispute with Venezuela, by threatening war. Britain gave in, implying that by this point Europe recognized the Monroe Doctrine as a real thing that they had to acknowledge. (Source)

The 20th Century: Mighty Morphin' Monroe Doctrine

The Roosevelt Corollary of 1905 was the last major expansion of the Monroe Doctrine's meaning, fully transforming it from a statement against European imperialism to a declaration of American sovereignty in the western hemisphere. Throughout the 20th century, the U.S. repeatedly got involved in Latin American affairs, though often a bit more covertly than in the old days. America helped various groups rebel against totalitarian governments…although the new leaders didn't always turned out to be any better.

After the World Wars, the U.S. also became less isolationist, putting aside that part of the Monroe Doctrine about not getting involved in European affairs. Instead, the part of the Roosevelt Corollary about being an "international police power" has become more popular. In fairness, the U.S. often works with other countries in their police duties. It's all much more complicated these days.

The U.S. involvement in the affairs of Latin America (and other parts of the world) is the topic of infinite books and articles. It's a pretty controversial history, and there are many who resent American involvement, and blame the U.S. for modern-day problems in a number of Latin American countries. There's a lot of truth to that idea.

The End of an Era

In 2013, secretary of state John Kerry declared that "the era of the Monroe Doctrine is over." (Source)

Even well into the 21st century, the Monroe Doctrine's influence was recognized. James Monroe could hardly have predicted the legacy of those few paragraphs when he made his brave stand against non-existent European imperialism almost two hundred years ago.

There's got to be a lesson in there somewhere.