In 1845, an American columnist, John O'Sullivan, writing about the proposed annexation of Texas, claimed that it was America's "manifest destiny to overspread the continent." Later in the same year, referring to the ongoing dispute with Great Britain over Oregon, he wrote that the United States had the right to claim "the whole of Oregon."
And that claim is by the right of our Manifest Destiny to overspread and to possess the whole of the continent that Providence has given us for the development of the great experiment of liberty and federated self-government entrusted to us.
The westward expansion did not originate with O'Sullivan's theory. In 1803, the United States acquired 23 percent of its existing territory through the Louisiana Purchase. Seeing land as a source of political power, the government began to actively pursue aggressive expansion of its territories through the 19th century. The idea of Manifest Destiny was one component of the process which captured the popular imagination. This was further fueled by the discovery of gold and other minerals in the West attracting Easterners acting on their conviction in their right and duty to expand.
The Mexican-American conflict generated massive casualties, and when it was over, the US controlled all of New Mexico and California, and more of the territory of Texas. When Texas was annexed in 1846 as the 26th state, Col. Ethan Allen Hitchcock wrote, "We have not one particle of right to be here."
Acclaimed historian Howard Zinn told Truthout, "The Mexican War, presented as something we were doing because Mexicans had fired on our soldiers ... no, we were going to Mexico because we wanted to take forty percent of Mexican land. California, Arizona, Nevada ... all of that beautiful land in the Southwest that was all Mexico. I'll bet there are very few Americans today who live in that area and know that it belonged to Mexico. Or they may ask, how come all these names? How come Santa Barbara, Santa Rosa, Santa Ana, how come?"
Perhaps Americans seriously believe that the US was preordained by God to expand and exercise hegemony over all that it surveys? After all, our 25th president, William McKinley, (1897-1901) declared that "The mission of the United States is one of benevolent assimilation."