The annexation of the Hawaiian Islands by the United States in 1898 was due to a combination of factors that converged during the turmoil surrounding the war with Spain. Although the annexation of Hawaii had been contemplated before the Spanish-American War - President Cleveland had sought to annex Hawaii in 1893, but the proposal failed to gain the necessary votes in Congress - there was significant opposition within the country prior to 1898.
During the 19th century Protestant missionaries from the United States began their work in Hawaii. As with China (where U.S. missionaries were also seeking converts), the presence of U.S. citizens in the foreign nation of Hawaii required a commitment by the United States to provide them with protection.
Also during the 19th century, entrepreneurs from the United States established lucrative sugar plantations in Hawaii - A 'barren land'? Nothing of the sort! Again, the safety of these U.S. citizens, along with their private property, was guaranteed by the U.S. Government.
Lastly, the increasing power and ambitions of a newly modernized Japan became a growing concern for political, military, and commercial leaders in the United States. Following Admiral Perry's ending of Japan's self-imposed isolation in 1854 and the Meiji Restoration in 1868, Japan underwent a process of rapid, full-scale adoption of Western technology, building a modern Army and Navy. With her new found military strength, Japan exerted her influence in Asia and the Pacific. Thus, the United States' worried that Japan might seize control of the Hawaiian Islands, giving the Japanese a strategically valuable position within the Pacific Ocean.
The Spanish-American War was the deciding factor for the question of whether or not the United States should annex Hawaii. President McKinley reluctantly went to war with Spain over Spanish rule in Cuba. But the U.S. Asiatic Squadron - the U.S. naval forces stationed in Asia for the protection of the lives and property of U.S. citizens in that part of the world - was ordered to attack Spanish naval forces located in Manila Bay, the Philippine Islands being a Spanish colony.
The end of Spanish rule in the Philippines presented the United States with a dilemma; what should be done with the Philippines? Even if President McKinley wanted to hand control of the Philippines over to Filipino patriots (who, like the Cubans, had been fighting against the Spanish for years), it was feared that the Filipinos would be unable to resist the modern military forces of a nation, such as Japan, that sought to make the Philippines their colony.
Therefore, like it or not, the leaders of the United States believed that they were faced with two unappealing, but distinct options. Either the the United States could risk the possibility of allowing another nation, possibly Japan, to increase its influence in Asia by seizing the Philippines or the United States could prevent this possibility by taking control of the Philippines, which would increase the influence of the United States in Asia.
The United States had major commercial interests in Asia, specifically, access to markets in which to sell the goods manufactured in U.S. factories. It should come as no surprise, therefore, that the leaders of the United States favored the option of keeping the Philippines for the U.S.
In order to understand why the U.S. annexation of the former Spanish colony of the Philippines led to the annexation of Hawaii (and the island of Guam), one has to understand the nature of late-19th century warships. The modern warships used during the time of the Spanish-American War were powered by steam engines that relied on coal for fuel. While it was possible to refuel warships at sea, it was difficult, time consuming, and, therefore, left the warships vulnerable during the process of taking on coal. It was both simpler and safer to fill a warship's coal bunkers with fuel in a protected harbor. In other words, a global naval power needed secure ports where their warships could be safely refueled.
The Philippines were a long way away from the nearest U.S. naval base on the West Coast of the United States. It was vital, therefore, if the United States was going to keep the Philippines as a colonial possession, that the U.S. Navy had access to refueling bases between California and the Philippines. Given that there were already elements within U.S. society and the U.S. Government who were calling for the annexation of Hawaii, the argument that the Hawaiian Islands were now strategically vital for the nation tipped the argument in favor of annexation (as did the likelihood of annexing the former Spanish colony of the Philippines, which established the precedent of the United States taking control of overseas territory). Those in favor of the annexation of the Hawaiian Islands pointed out that if another nation, such as Japan, took control of Hawaii, their warships based there would be in a position to interfere with the movement of warships or merchant ships traveling between the United States and the Philippines.
The question essentially came down to 'Which would the United States prefer? For the United States to dominate the Pacific pathway to the markets of Asia or allow some other nation, likely Japan, dominate this pathway and, thus, deny it to the United States.' For the people of the United States in 1898, the answer was clear.
