This is all information taken from a lesson plan that I wrote on Manifest Destiny for a US 1 class, but I think it should answer your question fairly well.

Reforms to Government- Kamehameha III, a son of Kamehameha I, took power in 1819. He sent delegations to the United States and European countries to pressure them to recognize Hawaii as a sovereign, independent country (which they did). Starting in 1840, he led a series of reforms to the structure of government and land ownership in Hawaii. This included a policy establishing private land ownership (in 1840) and a law that allowed foreign citizens to own land for the first time (passed in 1850). With this change in law, white planters (many of which were the descendants of missionaries) bought massive amounts of farmland, often for very little money, to use for sugar cane production. Within a few decades, a small group of white American and European planters controlled four-fifths of the arable (useable to grow crops) land in Hawaii.

Bayonet Constitution- A group of mostly American businessman living in Hawaii formed the Hawaiian League (aka the Annexation Club) to push for American annexation of Hawaii. In 1887, they lead an uprising against King Kalākaua. They threatened violence and forced him to sign a new constitution that greatly reduced his powers—this was referred to as the “Bayonet Constitution” since he agreed under massive pressure. The new Constitution transferred almost all power to members of the Hawaiian League, who made themselves government officials.

Hawaiian League Coup- King Kalākaua died in 1890 and his sister Lili‘uokalani became queen. Queen Lili’uokalani supported efforts to revise and strengthen the Constitution. She wanted to give voting rights to Hawaiians, take away voting rights of non-Hawaiians, and return power to the monarch by requiring the Queen to sign any proposed legislation before it became law. However, in January 1893 the Hawaiian League lead a coup d’état against Queen Lili’uokalani with the assistance of 162 U.S Marines, successfully overthrowing her. They proclaimed the establishment of the Republic of Hawaii and worked with a U.S. government official in Hawaii who immediately recognized them as a legitimate provisional government. When Grover Cleveland became U.S. president in March of 1893, he refused to recognize the provisional government and sent an investigator to Hawaii. Eventually, Cleveland decided that the provisional government was not legal but left the decision of whether to restore Queen Lili’uokalani to her throne up to Congress. They did not take any action.

American Territory- Four years later, in March of 1897, William McKinley, who was in favor of annexing Hawaii, became president of the U.S. He supported a treaty that would annex the territory, but it was not supported by the necessary two-thirds of Congress. The Hui Aloha ‘Āina, a group of Hawaiians opposed to annexation, held a mass meeting to protest annexation. They also began a petition drive to gather signatures of Hawaiians opposed to annexation. Between late 1897 and early 1898 representatives from Hui Aloha ‘Āina and Queen Lili’uokalani travelled to Washington, D.C., to present the petition and arguments against annexation to U.S. Senators. The Spanish-American War began in February of 1898, with the U.S. fighting in both Cuba and the Pacific. Several members of Congress changed their minds in favor of annexing Hawaii because they wanted to secure a fueling station and military base in the Pacific. A joint resolution to officially annex Hawaii passed in the U.S. Congress in July of 1898 and was signed by President McKinley and on August 12, 1898 “Annexation Day” was proclaimed and a ceremony was held to lower the Hawaiian flag and raise the American flag at the palace.

Hope this helps and can give you a basic outline of the annexation of Hawaii and the earlier events that made it possible.

Sources:

The Island Edge of America : a Political History of Hawai'i by Tom Coffman

Who Owns the Crown Lands of Hawai`i? by Jon M. Van Dyke