In December of 1823, President James Monroe gave an outline for future United States foreign policy—what later became known as the Monroe Doctrine. The US would establish itself as the protectors of free trade and democracy, especially in the Western Hemisphere. As such, the US would disavow the creation of European colonies in the Western Hemisphere, although an exception was made for pre-existing colonies. The US would remain neutral towards Europe, but any European expansion in the Western Hemisphere would be considered a threat to the US. As the US became more powerful militarily and its interests evolved, multiple corollaries to the Monroe Doctrine were formed. The Polk, Grant, and Olney Corollaries acted as both continuations of and deviations from the Monroe Doctrine.

The Polk Corollary of 1845, while adhering to the original principles of the Monroe Doctrine, expanded the kinds of European interference that the US considered as threats, as well as how the US would respond to such threats. The Polk Corollary reaffirmed many of the principles stated in the Monroe Doctrine, such as the insistence on no new European colonies. President Polk even referred to his reiteration of this policy as a “promulgation”; in other words, an announcement that the policy will be put into effect. However, the Polk Corollary deviated from the Monroe Doctrine by redefining a threat to include foreign intervention to prevent annexations. In the Monroe Doctrine, the US only defined explicit colonization as a threat to American interests. But Polk stated, “Should … an independent state … propose to unite themselves with our Confederacy, this will be a question for them and us to determine without any foreign interposition. We can never consent that European powers shall intervene to prevent such a union.” Additionally, the Polk Corollary deviated from the Monroe Doctrine by threatening force against such a threat. Up until this time, the US did not have sufficient military forces to truly enforce the principles articulated in the Monroe Doctrine. The Doctrine, in effect, had been not much more than a list of foreign policy aspirations. However, the Polk Corollary declared that European powers should not “cherish the disposition to resist” the Doctrine’s principles and that doing so would be met “with greatly increased force”, giving the US the ability to enforce the Doctrine. Thus, the Polk Corollary of 1845 adhered to the anti-intervention values of the Monroe Doctrine, but it also expanded the scope of European interference that the US considered a threat and declared that the US would respond to such threats with force.

The Grant Corollary of 1870 deviated from the Monroe Doctrine by further limiting European influence in the Western Hemisphere, while upholding the original principle of tolerating pre-existing colonies in the Monroe Doctrine. President Grant deviated from the original doctrine by becoming more strict on European powers, specifically on their ability to transfer colonies to one another. Grant asserted that “no territory on this continent [European or American] shall be regarded as subject to transfer to a European power”. Therefore, European powers that possessed North American colonies were left with two options: keep the colonies—which continued the principle set in the Monroe Doctrine—or surrender control to the territories, ideally to the United States to allow for US expansion. The Grant Corollary was a deviation from the Monroe Doctrine by restricting European ability to transfer territories to each other, yet also reaffirmed the tolerance of pre-existing colonies.

The Olney Corollary of 1895 continued to condemn new European colonies but deviated from the Monroe Doctrine by using more aggressive language indicative of US military strength. In the original Monroe Doctrine, the US had very little serious military backing to uphold the values espoused in the address. However, much had changed by 1895. Secretary of State Olney described the US as “practically invulnerable against any or all other powers” at the time of his statement, due to “its infinite resources” and “its isolated position”. This isolation in particular is precisely why Olney believed the sole threat against the US—also identified as a threat in the original Monroe Doctrine—was the emergence of European colonies in the Western Hemisphere. Olney explained, “All the advantages of this superiority are at once imperiled if the principle be admitted that European powers may convert American states into colonies or provinces of their own.” The Olney Corollary utilized the new global power status of the US to defend a key principle of the Monroe Doctrine.

The Polk, Grant, and Olney Corollaries both continued and deviated from the foreign policy aspirations outlined by the Monroe Doctrine. The Polk Corollary, while adhering to the original ideas in the Monroe Doctrine, expanded what European interference the US considered as threats, as well as how the US would respond to them. The Grant Corollary limited European colonial transfers in the Western Hemisphere while continuing to accept pre-existing colonies as mandated in the Monroe Doctrine. The Olney Corollary further condemned new European colonies while using more aggressive language indicative of new US military strength. Evidently, all three Corollaries reflect the ever-changing nature of American and global politics.