The Hawaiian Islands were annexed on july 7th, 1898 and became a state in 1959.
In 1887 a U.S. Naval Base at Pearl Harbor was build under the new Hawaiian constitution. Also during that time Hawaii supplied the united states 1/10th of it´s sugar.
In 1891 King Kalakaua died and his sister Liliuokalani became Queen. Queen Liliuokalani refused to recognize the new Constitution and made one of her own which would broaden her powers .
1893 Stanford Dole stages a coup on the queen with support of the United States out of fear of a devastating tariff on sugar. On February 1st 1893 a minister recognized Hawaii as a US protectorate.
Dole would send a treaty of annexation to congress where democrats furious would oppose it. President Cleveland would send a new minister to Hawaii to try to restore the throne to the queen but dole would refuse.
In 1898, President McKinley knowing the strategic position of pearl harbor convinced congress to annex Hawaii and two years later Hawaii became a US territory and in 1959 Hawaii became a state.