Final answer:
The statement is true; Hawaii was indeed a sovereign and independent kingdom until it was overthrown and later became a U.S. state in 1959.
Step-by-step explanation:
The question is whether Hawaii, which joined the U.S. in 1959, is the only American state that was once a kingdom. The statement is true. Hawaii was indeed a sovereign and independent kingdom from 1810 to 1893.
The monarchy was overthrown in 1893 and the islands were annexed by the United States as a territory, later becoming the 50th U.S. state in 1959. Key figures in the history of independent Hawaii include Queen Lili'uokalani, the last ruler, who was overthrown following attempts by American businessmen to protect their sugar interests.
The establishment of Hawaii as a U.S. territory in 1900, followed by statehood, had massive implications for the native Hawaiian population and culture, as well as for the strategic military presence of the U.S. in the Pacific.