Hawaii is a U.S. state and the only U.S. State that is in Oceania. It is the last state that joined the United States, becoming a state on August 21, 1959. It is the only state made only of islands. Hawaii is also the name of the largest island. The capital and largest city of Hawaii is Honolulu on the island named Oahu. Hawaii is an archipelago, a long chain of islands. There are eight main islands and many small islands and atolls. They are the tops of underwater volcanos. The main islands are Niihau, Kauai, Oahu, Molokai, Lanai, Kahoolawe, Maui and Hawaii.