The late 1800's and early 1900's, is a period in which the most powerful nations in that time such as the United States, Spain, Great Britain, Germany, France, wanted to gain more power and show the world who was the most powerful of the world. So the United States went through an era of imperialism. At the time, the U.S. was quite powerful, but was looking to continue to spread their territory, make themselves even stronger, and have multiple trade routes to have all the resources they needed and wanted. To obtain all of that, these powers believed that they should established overseas colonies. For example, France established in IndoChina, Britain in India, Australia and took control of the East coast of China, Spain had colonies in Latin America, the Philippines. And later the U.S. also started to establish colonies. They acquired territories such as Hawaii, Alaska, Panama, the Philippines, Cuba, etc. Many people think that U.S. imperialism was justified, but many others were totally opposed with it.
The United States needed to imperialize for economic and military reasons. In his book, The Interest of America in the Sea Power, U.S. Navy officer, Alfred T. Mahan, explained why he supported and why the U.S. needed to imperialize. He stated: "America must begin to look outward. The growing of the country demands it. " So the U.S. had to begin to look outward to grow and find new markets. For example, they acquired Hawaii, in order to build a Navy (Pearl Harbor) and also because of the sugar. In this case, they made a revolution, overthrew the Queen and took control of Hawaii. The U.S. government and military were glad to have Hawaii and also the Sugar planters wanted to annex Hawaii to the U.S. to don't have to pay the tax. Another example here is Panama. The U.S. was interested in building a Canal in Panama to have multiple routes for commerce. In that time, Panama was controlled by Colombia so the U.S. had first to help Panama to gain its independence and then start trading.
