Final answer:
Hawaii is the U.S. state in the middle of the Pacific Ocean, strategically annexed for its location and awarded statehood in 1959. Alaska, California, and Texas, though important, are not situated in the Pacific.
Step-by-step explanation:
The state that belongs to the United States but lies in the middle of the Pacific Ocean is Hawaii. Hawaii was annexed by the United States due to its strategic location during the Spanish-American War. It served as a mid-point between the newly acquired Philippines and the Central American canal. Hawaii was given traditional territorial status in 1900, granting residents American citizenship and the authority to elect a legislature. In 1959, Hawaii was admitted to the Union as a state, along with Alaska. Alaska, California, and Texas, while geographically significant to the U.S., do not fit the description as they are not in the middle of the Pacific Ocean.