Hawaii was important to US expansionism first because it was the country’s first major overseas acquisition and second because it helped the US with both of its main reasons for expanding.
Military power and economic gain were the two most important reasons for expansion. Hawaii gave America both of these things. The Hawaiian sugar plantations were a great source of wealth and of sugar, which is one reason why sugar magnates were behind the overthrow of Queen Lili’uokalani. When the US took Hawaii, the Navy got a large and important base at Pearl Harbor. This helped the US to project its power across the Pacific.
Soon after the Civil War, the United States felt the need to expand its orders and was interested in overseas colonies. The countries of Europe had ventured into Africa to acquire colonies to fuel their industrial ambitions. Many in the United States felt that to compete on the international scale, the acquisition of overseas colonies was necessary.
American businessmen in Hawaii realized the lucrative nature of the sugar trade on the island. They attempted to westernize Hawaii and eventually would overthrow a monarchy that they had installed earlier. In 1897, a group of native Hawaiians petitioned Congress to block the annexation of Hawaii that was being proposed by President Benjamin Harrison. The effort was successful as Congress refused to annex Hawaii.
Further efforts at imperialism were made by the United States in Cuba that would change Congress's view of the Hawaiian situation. The United States was at war with Spain in Cuba and the Philippines. Hawaii was of importance to the military effort because of its location. The U.S. Navy needed the islands for refueling ships that were en route to the Philippines. It was at this time that Congress annexed Hawaii because of the economic and military benefit the islands offered.
One of the biggest reasons why the US wanted Hawaii was a similar reason for its imperialism- acquire strategic military bases. Because Hawaii is much further out into the Pacific Ocean, it provides the US with a military base closer to Asia. This came in handy during WWII, at the Pearl Harbor naval base, which was attacked by the Japanese on December 7, 1941. The base ended up being a crucial beginning point in our Pacific campaign against Japan.
Another reason the US wanted Hawaii was for its lucrative sugar trade. Hawaii was a large sugar producer, and the United States charged high tariffs for Hawaiian sugar merchants. By annexing with the United States, Hawaii no longer had to deal with tariffs, and the US could profit directly from Hawaiian sugar.