The later part of the 19th century marked a time when The United States would begin to re-evaluate it's position in the world. More and more Americans shared the feeling that the US needed to enhance it's status in the world to gain economic and military power, along with ideas that it was our duty to save the helpless people of the world.
One of the groups that supported the expansion of the US's powers were the Protestant Missionaries. These people were convinced that the Anglo race was superior to all others and it was their duty to save the souls of the ignorant barbarians, especially the Chinese and Asians. They believed that through the spread of Christianity these people would no longer be doomed to their racial destiny and they would become civilized.
During this period businessmen also began to look abroad for opportunities to enhance their fortunes. Amoung these businessmen were traders, industrialists, and investors who saw the expansion of US power as a way to enter new markets. These feelings intensified when Fredrick Jackson Turner published his "frontier thesis." It basically stated that the US had completed it's domestic westward expansion and the frontier had dissapeared. He also stated that the frontier was essential to economic growth and democracy. Now that it was gone European immigrants would no longer be "Americanized," making it difficult for America to continue to grow and prosper. None the less American businessmen took advantage of these new opportunities and were able to enter foreign markets. One example is James Duke and his cigarettes. He was able to sell over 1 billion cigarettes in China per year, this generated a whole new stream of profits.
One other group of Americans that encouraged US expansion were the Imperialists. Unlike the other groups, their motives were to control lands and territories outside US borders in order to increase military power. The believed that the rightful place of the US belonged alongside and even above countries like France, Germany, and Russia. A large amount of these imperialists were Social Dawinists who saw America's destiny to be the master of the "lesser" people of the world. In order to achieve their goal it was obvious that the US need to improve it's naval power and flex it's muscle to the other nations.
All of these movements along with an increasing sense of Nationalism amoungst Americans pushed the policy makers of the US to move beyond traditional realms. This period was marked by the colonization of islands like Hawaii and the Philipines, along with the Spanish American war, which was intended to "liberate" the people of Cuba. All of these efforts succeeded in expanding the power and influence of the US, forcing other nations to acknowledge and respect our power.