Manifest Destiny was a phrase which invoked the idea of divine sanction for the territorial expansion of the United States. It first appeared in print in 1845, in the July-August issue of the United States Magazine and Democratic Review. The anonymous author, thought to be its editor John L. O'Sullivan, proclaimed "our manifest destiny to overspread the continent allotted by Providence for the free development of our multiplying millions."
The specific context of the article was the annexation of Texas, which had taken place not long before. Other applications of the notion of manifest destiny were soon found. It was used to promote the annexations of Mexican territory acquired in the Mexican-American War, of territory in Oregon gained through negotiations with the British, and the seizure (not carried out) of Cuba from the Spanish during the 1850's.
Various arguments against western expansion were put forward, particularly by those on the Eastern seaboard who feared a dilution of their influence on national affairs. It was suggested that a democratic government should not try to extend itself over such a vast territory. James K. Polk responded to this in his inaugural address in 1844:
In the earlier stages of our national existence the opinion prevailed with some that our system of confederated States could not operate successfully over an extended territory, and serious objections have at different times been made to the enlargement of our boundaries. These objections were earnestly urged when we acquired Louisiana. Experience has shown that they were not well founded. The title of numerous Indian tribes to vast tracts of country has been extinguished; new States have been admitted into the Union; new Territories have been created and our jurisdiction and laws extended over them. As our population has expanded, the Union has been cemented and strengthened. As our boundaries have been enlarged and our agricultural population has been spread over a large surface, our federative system has acquired additional strength and security. It may well be doubted whether it would not be in greater danger of overthrow if our present population were confined to the comparatively narrow limits of the original thirteen States than it is now that they are sparsely settled over a more expanded territory. It is confidently believed that our system may be safely extended to the utmost bounds of our territorial limits, and that as it shall be extended the bonds of our Union, so far from being weakened, will become stronger.
The philosophical support for manifest destiny was based on the idea that America was destined to expand democratic institutions in North America, which gave the nation a superior moral right to govern areas where other interests would not respect this goal. This was particularly clear with respect to Texas, and the alternative of a Mexican dictatorship, but it was also applied in the Oregon territory. Britain itself might be democratic, but that was not its purpose in Oregon.
The ill-fated Ostend Manifesto of 1854, which advocating Cuba from Spain either by cash purchase or force, was quickly abandoned. It demonstrated that while Manifest Destiny was a powerful force in American thinking when oriented west, it did not yet extend beyond the shores and definitely if it involved a future slave territory.
Manifest destiny was a popular and easily understood phrase, which was adopted by successive political parties. Originally the position of the Democratic Party, it was absorbed into the platforms of the Whig and later Republican parties. Even the Alaska Purchase of 1867 and acquisitions outside the continent, such as Guam and Hawaii, were promoted as examples of manifest destiny in action. Gradually, the phrase became seen as a cover for imperialism and political support has died out.