What is the largest island in the United States?

While many might guess an island in Alaska, the distinction of being the largest in the United States belongs to the island of Hawaiʻi. Popularly called the Big Island to avoid confusion with the state itself, it has a land area of over 4,000 square miles. This makes it significantly larger than the second-place contender, Alaska's Kodiak Island, and in fact, it is bigger than all of the other Hawaiian islands combined.

The island’s immense size is due to its dramatic volcanic origins. It is comprised of five massive shield volcanoes that have merged together over eons. Two of these, Kīlauea and Mauna Loa, are among the most active volcanoes on Earth. This constant geological activity means the Big Island is still growing, with lava from Kīlauea's eruptions regularly flowing into the ocean, cooling, and creating new land along the coastline.

This volcanic landscape gives the island another impressive geographical feature. It is home to Mauna Kea, which, when measured from its base on the ocean floor to its summit, is the tallest mountain in the world, surpassing even Mount Everest.