There were multiple reasons that the United States looked to expand beyond its borders in the late nineteenth and early twentieth centuries. Let us look at three of them.
- American industry demanded new markets. Overproduction was a constant fear among economists and businessmen in the late nineteenth century as manufacturing techniques became more efficient. American politicians therefore sought to open new markets for American manufactured goods in places like China.
- The United States needed naval bases around the world. If the nation was to expand its trading presence, it needed to expand its naval presence to protect its interests. This was a major factor in American expansion in the Pacific, a process that included the annexation of many small islands as well as the Philippines and Hawaii.
- The United States had a moral obligation to spread American culture, especially Protestant Christianity. The missionary zeal of many Americans should not be understated. It was especially a factor in the Philippines, where thousands of missionaries and modernizers descended on the islands after annexation. Christianity was important, but many had other motives, such as vaccinating natives against disease, constructing schools, and promoting what they saw as acceptable Western lifestyles.
It should be noted that these motives are far from mutually exclusive, indeed they went hand in hand. One could have economic and religious motives, for example.