Hawaii is the newest of the 50 U.S. states (August 21, 1959), and is the only U.S. state made up entirely of islands. It is the northernmost island group in Polynesia, occupying most of an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of Australia. Hawaii’s natural beauty, warm tropical climate, inviting waters and waves, and active volcanoes make it a popular destination for tourists, surfers, biologists, and volcanologists alike. Due to its mid-Pacific location, Hawaii has many North American and Asian influences along with its own vibrant native culture. Hawaii has over a million permanent residents along with many visitors and U.S. military personnel. Its capital is Honolulu on the island of Oʻahu.

Because the islands are so far from other land habitats, life before human activity is said to have arrived by the “3 W’s”: wind (carried through the air), waves (brought by ocean currents), and wings (birds, insects, and whatever they brought with them). This isolation, and the wide range of environments (extreme altitude, tropical climate) produced a vast array of endemic flora and fauna. Hawaii has more endangered species and has lost a higher percentage of its endemic species than any other U.S. state.

Location, topography, and geology Hawaii is the southernmost state of the United States; it would be the westernmost, if not for Alaska. It is one of only two states (Alaska is the other) that are outside the contiguous United States, and do not share a border with another U.S. state.

Hawaii is the only state of the United States that:

- Is separated from the mainland by water, yet is not a territory

- Is completely surrounded by water

- Continues to grow in area because of active extrusive lava flows, most notably from Kilauea (Kīlauea).

- Is entirely in the tropics.

Except for Easter Island, Hawaii is farther away from land than any other landmass on Earth. Hawaii’s tallest mountain, Mauna Kea stands over 13,000 feet (4,000 m) and is taller than Mount Everest if followed to its base at the floor of the Pacific Ocean.
All of the Hawaiian Islands were formed by volcanoes arising from the sea floor from a magma source described in geological theory as a hotspot. The theory maintains that as the tectonic plate beneath much of the Pacific Ocean moves in a northwesterly direction, the hot spot remains stationary, slowly creating new volcanoes. This explains why only volcanoes on the southern half of the Big Island, and the Loihi Seamount deep below the waters off its southern coast, are presently active, with Loihi being the newest volcano to form. The last volcanic eruption outside the Big Island happened at Haleakala (Haleakalā) on Maui in the late 18th century (though recent research suggests that Haleakala’s most recent eruptive activity could be hundreds of years older). The volcanic activity and subsequent erosion created impressive geological features. The Big Island is notable as the world’s fifth highest island.