The United States possesses some of the world\'s most spectacular island territories, from the volcanic wonders of Hawaii to the Arctic wilderness of Alaska. These diverse landmasses offer unique ecosystems, cultures, and landscapes that showcase America\'s geographic diversity beyond the mainland.
From tropical paradises to rugged northern territories, America's islands represent some of the most diverse and spectacular landscapes in the nation. While the mainland United States captures much of the attention, these island territories offer unique cultural experiences, rare ecosystems, and natural beauty that mainland visitors rarely encounter.
The largest islands in the USA span from the Arctic Circle to the Caribbean, each with its own distinct character shaped by geography, climate, and human history. Let's explore these remarkable island territories that represent some of America's most precious natural and cultural treasures.
Hawaii (Big Island)
At 4,028 square miles, Hawaii's Big Island is the largest island in the United States and continues to grow thanks to the active Kilauea volcano. The island showcases remarkable geographic diversity, featuring 8 of the world's 13 climate zones within its boundaries.
The Big Island hosts two massive shield volcanoes: Mauna Loa, the world's largest active volcano by volume, and Mauna Kea, which measures over 33,000 feet from its oceanic base to summit—technically making it taller than Mount Everest when measured from base to peak.
Visitors to the Big Island can experience everything from black sand beaches and tropical rainforests to snow-capped mountains and volcanic deserts. Hawaii Volcanoes National Park offers the rare opportunity to witness active volcanic processes reshaping the landscape in real-time.
Kodiak Island
The second-largest island in the United States, Kodiak Island encompasses 3,588 square miles off the southern coast of Alaska. This rugged wilderness is home to the famous Kodiak bears—the largest subspecies of brown bear in the world, with males weighing up to 1,500 pounds.
Nearly two-thirds of Kodiak Island is protected as the Kodiak National Wildlife Refuge, established in 1941 to protect the island's unique ecosystem and its approximately 3,000 Kodiak bears. The island's economy centers around fishing, with Kodiak Harbor ranking among the top fishing ports in the United States by value of catch.
Kodiak's history reflects a blend of Indigenous Alutiiq culture, Russian colonization, and American influence. The island's main community, the city of Kodiak, was established as a Russian fur trading post in 1792 and still maintains elements of this heritage in its architecture and culture.
Puerto Rico
As the third-largest island in the United States, Puerto Rico covers approximately 3,515 square miles in the northeastern Caribbean. This unincorporated U.S. territory combines Spanish colonial history, vibrant Taíno indigenous heritage, and African influences into a unique cultural identity.
Puerto Rico's diverse landscape includes the only tropical rainforest in the U.S. National Forest System—El Yunque—as well as stunning beaches, limestone cave systems, and the bioluminescent Mosquito Bay, considered the brightest bioluminescent bay in the world.
Old San Juan, with its distinctive blue cobblestone streets and Spanish colonial architecture, represents one of the best-preserved historic districts in the Americas. The island's status as a U.S. territory since 1898 has created a fascinating blend of American and Latin American influences across its culture, cuisine, and governance.
Prince of Wales Island
Located in Alaska's Alexander Archipelago, Prince of Wales Island ranks fourth among America's largest islands at approximately 2,577 square miles. This temperate rainforest island hosts some of the nation's most pristine wilderness and is part of the Tongass National Forest—the largest national forest in the United States.
The island features an extensive road system by Alaskan standards, with over 1,000 miles of roads providing access to remote fishing spots, hiking trails, and viewpoints. Prince of Wales Island is known for excellent salmon fishing, with all five Pacific salmon species available in its waters.
Indigenous Tlingit and Haida peoples have inhabited the island for thousands of years, and several communities continue to practice traditional ways of life alongside modern amenities. The island's economy relies heavily on fishing, timber, and increasingly, tourism.
Chichagof Island
The fifth-largest island in the United States, Chichagof Island covers approximately 2,048 square miles in the northern section of Alaska's Alexander Archipelago. The island has one of the highest concentrations of brown bears in the world, with a bear density estimated to be one per square mile—higher than the human population density.
Chichagof's communities are small and primarily accessible by boat or plane, with Hoonah being the largest settlement. The island's economy centers around fishing, logging, and tourism, particularly cruise ships visiting the nearby Glacier Bay National Park.
The island's rugged terrain features fjords, mountains, and dense forests that provide habitat for diverse wildlife, including deer, wolves, and eagles. Its relative isolation has preserved much of its wilderness character despite increasing tourism to the region.
Long Island
At approximately 1,401 square miles, Long Island is the largest island in the contiguous United States and the sixth-largest U.S. island overall. Located just east of Manhattan, this densely populated island is home to 7.6 million people—a stark contrast to the wilderness islands of Alaska.
Long Island stretches 118 miles from New York Harbor to Montauk Point, ranging from urban neighborhoods in the west to the famous Hamptons and wine country in the east. Despite its development, the island maintains significant natural areas, including Jones Beach State Park and the Montauk Point State Park.
Geologically, Long Island was formed by glacial moraines during the last ice age, creating its distinctive fish-tail shape and sandy soil composition. The island plays a crucial role in New York's economy and culture while offering seaside communities and beaches within reach of one of the world's largest metropolitan areas.
Unimak Island
The seventh-largest island in the United States, Unimak Island spans approximately 1,571 square miles at the eastern end of Alaska's Aleutian chain. This remote volcanic island hosts several active volcanoes, including Mount Shishaldin, one of Alaska's most active volcanoes with its nearly perfect conical shape rising to 9,373 feet.
Unimak is separated from the Alaska Peninsula by the narrow Isanotski Strait, sometimes called "False Pass" because it's too shallow for many vessels. The island lies within the Alaska Maritime National Wildlife Refuge and is home to diverse wildlife, including caribou, brown bears, and massive colonies of seabirds.
Human settlement on Unimak is extremely limited, with fewer than 100 residents. The island represents one of America's last true wilderness frontiers, where natural processes continue largely undisturbed by human activity.
Baranof Island
Covering approximately 1,607 square miles in the Alexander Archipelago of Southeast Alaska, Baranof Island ranks as America's eighth-largest island. The island is known for its extremely rugged terrain, with mountains rising steeply from the coastline to heights over 5,000 feet, earning it the nickname "The Norway of Alaska."
Sitka, the island's main community and former capital of Russian America, blends Russian heritage with Tlingit culture and American influence. The island receives extraordinary rainfall—over 100 inches annually in some areas—creating lush temperate rainforests and countless waterfalls.
Baranof Island features numerous hot springs, including Baranof Warm Springs and Goddard Hot Springs, where thermal waters reach temperatures up to 153°F. These geothermal features provide a stark contrast to the island's cool climate and glaciated peaks.
Maui
The ninth-largest island in the United States, Maui covers approximately 727 square miles in the Hawaiian archipelago. Known as "The Valley Isle" due to the isthmus between its two volcanic mountains, Maui combines luxury resorts with spectacular natural wonders and traditional Hawaiian culture.
Haleakalā, a massive shield volcano comprising 75% of the island, features a 10,023-foot summit with views above the clouds and a massive crater-like depression that resembles a lunar landscape. The volcano's name means "house of the sun" in Hawaiian, referencing the legendary capture of the sun by the demigod Maui.
The Road to Hana, a 64-mile highway featuring 620 curves and 59 bridges, showcases Maui's lush eastern coastline with waterfalls, black sand beaches, and bamboo forests. The island's western shores offer some of Hawaii's best beaches and premier whale-watching opportunities during winter months when humpback whales migrate to these waters. For summit access and current conditions, see Haleakalā National Park.
Admiralty Island
Rounding out the top ten largest U.S. islands, Admiralty Island encompasses approximately 1,646 square miles in Southeast Alaska's Alexander Archipelago. The Tlingit people call it "Xootsnoowú", meaning "Fortress of the Bears," reflecting its remarkable density of brown bears—estimated at 1,600, nearly one per square mile.
Almost 90% of Admiralty Island is protected as the Admiralty Island National Monument, preserving one of the largest intact temperate rainforests in the world. The island's Kootznoowoo Wilderness Area offers pristine habitat for not only bears but also bald eagles, with the highest concentration in North America.
Angoon, the island's main settlement, is home to about 450 people, primarily Tlingit, maintaining traditional subsistence practices alongside modern life. The island exemplifies the delicate balance between conservation and human use in one of America's most spectacular wilderness settings.
Protecting Island Ecosystems
America's largest islands face unique conservation challenges due to their isolation and distinct ecosystems. Island species often evolve in isolation, making them particularly vulnerable to invasive species, climate change, and habitat destruction.
Conservation efforts across these islands vary dramatically, from the strict protections of Alaska's wildlife refuges to the complex balance of development and preservation in more populated islands like Long Island and Puerto Rico. Rising sea levels pose an existential threat to many coastal areas, particularly in low-lying island territories.
Sustainable tourism initiatives have become increasingly important for island economies seeking to protect their natural resources while benefiting local communities. From Hawaii's efforts to manage visitor impacts to Puerto Rico's development of ecotourism alternatives, these approaches aim to preserve island ecosystems for future generations.
America's island territories represent some of the nation's most precious natural resources and cultural treasures. Their protection requires thoughtful policies that recognize their unique challenges and irreplaceable value to the nation's natural heritage.
Frequently Asked Questions About 10 Largest Islands in the USA: Stunning Island Territories You Need to Explore
Which is the largest island in the United States?
Hawaii's Big Island (Island of Hawaii) is the largest island in the United States, covering approximately 4,028 square miles. It continues to grow in size due to ongoing volcanic activity from Kilauea volcano.
How many of the largest US islands are in Alaska?
Six of America's ten largest islands are located in Alaska: Kodiak Island, Prince of Wales Island, Chichagof Island, Unimak Island, Baranof Island, and Admiralty Island. Alaska's numerous islands are primarily concentrated in the Alexander Archipelago in the southeast and the Aleutian Chain extending westward.
Are all of these islands states or territories of the US?
Not all are states. Hawaii's islands are part of the state of Hawaii, and Long Island is part of New York state. The Alaskan islands are part of the state of Alaska. Puerto Rico, however, is a U.S. territory with commonwealth status, not a state.
What makes island ecosystems unique?
Island ecosystems are unique because their geographic isolation allows distinct species to evolve separately from mainland populations. This isolation creates higher rates of endemism (species found nowhere else). Islands often have fewer predators and competitors, allowing unique ecological relationships to develop. This uniqueness also makes island ecosystems particularly vulnerable to invasive species and habitat changes.
Which of these islands is most accessible for tourists?
Long Island is the most accessible for tourists, being connected to New York City by bridges, tunnels, and public transportation. Hawaii's islands and Puerto Rico are also highly accessible with major international airports serving millions of visitors annually. The Alaskan islands are generally more difficult to reach, often requiring small aircraft or boat transportation.
What wildlife is unique to these islands?
Each island has distinctive wildlife: Hawaii features species like the nene goose and happy-face spider. Kodiak Island is famous for the Kodiak brown bear, the largest subspecies of brown bear. Puerto Rico has the small coquí frog found nowhere else. Alaska's islands host dense populations of brown bears, eagles, and unique subspecies adapted to their temperate rainforest environments.
