Why The US Became An Imperialist Power It can certainly be argued that the turn to imperialism by the United States in the late nineteenth century was of a piece with expansionist policy that dated back to the founding of the nation. Many of the justifications were similar, including a civilizing mission, expanding economic opportunities, competition with foreign powers, and others. Additionally, the anxieties that resulted from the closing of the frontier (most famously expressed in Frederick Jackson Turner's 1893 essay The Significance of the Frontier in American History) are often cited as driving forces for continued expansion as a way of maintaining American vitality in a modern world. Yet imperialism marked a major departure from previous US policy. For more than a century, political leaders had emphasized American isolation from the problems of the world. By mid-century, however, the desire for new markets for United States manufactured goods had resulted in increasing involvement in foreign affairs. The United States became an imperialist power for reasons of wealth, land, and power in the late eighteenth century. Though ideologically convincing, the imperialist policies that the US followed proved to be unsuccessful in a number of instances. From 1890 to about 1911, many Americans held the strongest of reservation either in favor or against United States imperialism. Thus, the debate over imperialism is split into two categories: Imperialists and anti-imperialists. The debate surrounding imperialism was indeed one of the greatest hot-button issues for the time. Imperialists felt that the taking over of other, smaller, countries would open new markets to the United States, which would, in-turn, generate a larger economy for the US. Access to raw materials, such as Cuba’s marketable coffee and cigars, would be a great advantaged given to the United States