Largest Islands In The United States

Statue of Liberty, New York, US. Image credit: Rujipart/Shutterstock
  • Hawaii's Big Island houses Kilauea, the world's most active volcano, as well as Mauna Loa, the world's largest volcano that is known for spectacular eruption displays.
  • Prince of Wales Island was largely overlooked by westerners until the discovery of gold in Alaska in the late 1800s.
  • Campers in the wilderness area of Chichagof Island can enjoy the view from the cliffs overlooking the pounding waves at the bottom.

No two islands in the world, or even just in the United States, are the same. Since most islands were once joined to the mainland, they follow their state's environmental features. For instance, the Alaskan islands follow suit with a colder humid climate, while the Hawaiian islands feature a mix of tropical and dry heat. Nevertheless, their comparatively smaller size and being completely embraced by water give islands a unique character. The islands' location also plays a big role in the island's features, human activity, and environmental characteristics.

Here are the five largest islands in the US:

1. Hawaii Island (The Big Island) - 10,433 Km2

Waipio Valley, Hawaii Island, Hawaii, US. Image credit: Leena Robinson/Shutterstock

According to Mark Twain, the "loveliest fleet of islands that lies anchored in any ocean," Hawaii today is a prosperous state made up of eight islands and 124 islets connected by lava saddles. Although the state's capital is Honolulu on Oahu Island, it is the state's namesake volcanic island, Hawaii, that is the largest. This island hosts the most unique landforms in the world. It is also the youngest of the big islands. 

The Big Island is home to five volcanoes: Hualalai, Kilauea, Kohala, Mauna Kea, and Mauna Loa. The last two are the main features of the Hawaii Volcanoes National Park, a World Heritage Site. The world's largest volcano, Mauna Loa, erupts in spectacular displays. In contrast, the lava from the most active volcano globally, Kilauea, continuously expands this triangular island's south-western edge as lava solidifies in the coastal waters. The snow-capped Mauna Kea is the tallest mountain in the state, at 4,205 meters. The volcanoes formed when the Pacific Plate transited over the regions where the Earth's upper mantle upwells closer to the surface beneath the central Pacific Ocean, also known as hotspots. As the contents of Earth's interior melted up through the outer crust, the erupting magma created the islands that today make up Hawaii.

Other topographical features of the island include plateaus, ocean cliffs, coastal tropical areas, lava deserts, and fern and bamboo forests. At the mercy of natural forces for millions of years, the older areas feature deep valleys, collapsed craters, and coastal plains. The eroded mountains tower with their sharp and craggy silhouettes of abrupt vertically grooved cliffs and many caves. The younger areas retained a smooth, dome-like terrain. The predominance of volcanoes on the eastern side of the island protects the western region from humid winds while making it prone to dry climate. Water influx known as the Pacific Surf, created by the west-bound ocean winds, carries reduced coral and all sizes of seashells from the deep waters and up onto the famous beaches. 

Excess rainfall collects in the many valleys on the island and within the porous mountain surfaces, while the underlying saltwater prevents it from seeping into the ocean. As a result, the island is rich in artesian water used for agricultural purposes and as a drinking water supply for the people.

The rich culture and warm climate on the island are magnets for tourists. The thriving manufacturing and agricultural sectors are the other two pillars of the economy. Its strategic location also makes Hawaii an indispensable defense base for the United States. Its volcanic composition and ocean access allow it to delve into research and development of oceanography, geophysics, astronomy, satellite communications, and biomedicine as one of the world's leading players. 

2. Kodiak Island (Alaska) - 9,239 Km2

Kodiak Island, Alaska, US. Image credit: K.C. Goshert/Shutterstock

Lying in the Gulf of Alaska, Kodiak Island is 50 km away from the coast and separated from the Alaskan Peninsula by the Shelikof Strait. It is also 250 km away from Alaska’s biggest and most populated city, Anchorage. Along with Afognak, Shuyak, and some smaller islands, it is part of an archipelago extending the Kenai Mountains. 

Although first explored by a Russian in 1763, the island got its name from the famous English explorer James Cook in 1778. The first settlement was established by another Russian, hunting seals in 1784, and in 1867 the Russian control of the island ended when we purchased it with the rest of Alaska. Due to its immense fishing stock, the island experienced an influx of people in the late 19th and early 20th centuries. Today, it is also home to a satellite launch center, while the northeast part of the island contains the Fort Abercrombie State Historical Park, the grounds of a naval base during the Second World War. 

Kodiak Island's topography consists mostly of uplands, with its forest-covered eastern coast reaching 1,500 meters (5,000 ft). At lower elevations where glaciation did not cover the surface, one will find sand and gravel, while moist tundra dominates the south-western lower portion of the region. The climate and flora vary widely, while the largest brown bear on Earth, the Kodiak bear, is native to the island, with a population of around 3,000 today. Being volcanic in nature, the ash from the explosion of the Novarupta Volcano in 1912  helped the island's natural vegetation flourish. 

In 1989, the fishing industry incurred serious damage when the Exxon Valdez oil tanker ravaged the beaches, causing a massive oil spill in the Gulf of Alaska, northeast of the island. 

3. Puerto Rico - 8,710 Km2

El Morro fortress, Puerto Rico Island, US. Image credit: Gary Ives/Shutterstock

Though the Commonwealth territory of Puerto Rico actually consists of 143 islands and islets, Puerto Rico island, the biggest and main population center, is a 179 by 63 km rectangular island known for its mix of American, Caribbean-African, and Spanish cultures. It is socially and economically advanced compared to other Latin places, partly due to its well-developed tourism and partly because of its union with the US.

A quarter of Puerto Rico is covered by steep hills, while the mountains stretching on its eastern edge are an extension of the Central American range, once co-joined all the way to the Lesser Antilles. The highest mountain range on the island, Cordillera Central, is gently sloped but exceeds 900 meters (3,000 ft) in height at multiple points, with the highest, Cerro de Punta, reaching 1,338 meters (4,390 ft), and Sierra de Luquillo, 1,065 meters (3,494 ft). 

There are many sinkholes, caverns, and eroded haystack hills in the north-western foothills of Puerto Rico. The largest canyon, The Caguas Basin, is south of the capital, San Juan. Providing both the valley's flatlands and access to the waters of the Grande de Loiza River, it is an optimal spot for agricultural and other settlement activities.

Most people reside along the north coast, known for its long stretch of narrow lowland. Small batches of similar terrain along the south and west coasts are also populated. Most of the islands are characterized by a hilly interior and narrow, flat coastlines. 

Another interesting feature of the island is that it is situated not far south of a precipitous depression in the Earth's crust, created by tectonic forces over millions of years. Also known as the Puerto Rico Trench, it sits more than 5 miles below sea level, making it the deepest point of the Atlantic Ocean. 

4. Prince Of Wales Island (Alaska) - 6,675 Km2

Prince of Wales Island, Alaska, US. Image credit: Andrea Izzotti/Shutterstock

Prince of Wales Island is defined by a temperate rainforest climate, with relatively cool temperatures and abundant rainfall. With a meandering coastline of almost 1,609 km (1,000 miles), kayakers and other paddlers can shore and make use of the public cabins in the Tongass National Forest. Well-paved roads, such as the Hollis-Klawock Highway, as well as mountain bike trails, allow for a comfortable starting point for further exploration inland. Among numerous scattered villages, the island's most populated towns are Craig and Klawock, followed by Thorne Bay and Coffman Cove. 

Although the island's primary residents were the Tlingits, the majority of today's population is of the Kaigan Haida descent from their settlement in the area back in the 18th century. Briefly visited by European explorers in the 1700s, the island was largely overlooked by westerners until discovering gold in Alaska in the late 1800s. Known for its vast ruggedness, Prince of Wales Island is also a destination for explorers, hikers, and backpackers.

Once a booming logging and timber-harvesting industry, the depletion of the island's rich Sitka Spruce and Western Hemlock reserves in the span of just a few decades at the end of the last century changed the island's economic focus to fishing, the island's main economic driver to this day. Rich in salmon and halibut, the island also attracts fishing enthusiasts. In the forests, black bears are commonly-sighted wildlife on the island. 

5. Chichagof Island (Alaska) - 5,388 Km2

Located in the northwest corner of the Alexander Archipelago of Southwest Alaska, its western side is known for the extreme wilderness of Western hemlock and Sitka spruce forests, home to Sitka black-tailed deer, Brown bears, among other wildlife. The wilderness is controlled by the US Forest Service, which allows camping and even installs four rental cabins for travelers. The other side of the island is covered in vegetation, including muskeg, alpine, and estuarine. 

The wilderness ends in cliffs that open up dramatically over the Pacific Ocean. The pounding waves against miles of rocky sides are juxtaposed by calmer bays and islands that provide a safe harbor for sailors and trackers. Small in size but large in numbers, the migratory waterfowl fly over these areas. Hunted by the island's early residents, sea otters, sea lions, and seals are commonly sighted in the waters. 

Before the Russians came, the island was home to First Nations populations, who used its rich natural resources for food and shelter-building. Formerly known as the island "Yakobi," which translates "seems to be so" from Russian, it was renamed in 1805 by Captain U. F. Lisianski of the Imperial Russian Navy to its present-day name, after the Russian explorer Admiral Vasili Yakov Chichagov who explored the region in 1765-66. The name "Yakobi" was transferred to the neighboring island. One million ounces of gold were unearthed in the following two centuries, with the evidence of mining sites remaining today. 

Distribution Of Islands In The US

The US owns 18,617 islands, with Alaska claiming nearly one-sixth of the total with over 2,600 islands to its name. All but one of the top 50 islands by size also belongs to Alaska's state (New York's Long Island is the exception, at #11). 

Most islands in the world formed through either continental drift millions of years ago that separated chunks of earth from the mainland or through erosion and build-up of material, such as forming the Hawaiian islands from solidified magma. Places with historically strong tectonic activity spurred many islands, as is the case with Alaska, where well over 1,000 islands make up the Alexander Archipelago. 

Human activity also determines the use of and activity on the island. Whereas many Alaska islands are barren or sparsely populated, Long Island follows demonstrates New York's modernity, business, and fashion. On the other hand, many islands are rich in natural resources, and the climate goes into the backdrop when it comes to human migration for harvesting those resources.

Largest Islands In The United States

RankIslandArea (km2)Location
1Hawaii Island (the Big Island)10,433Hawaii
2Kodiak Island9,293Alaska
3Puerto Rico8,710Puerto Rico
4Prince of Wales Island6,675Alaska
5Chichagof Island5,388Alaska
6St. Lawrence Island5,135Alaska
7Admiralty Island4,362Alaska
8Nunivak Island4,209Alaska
9Unimak Island4,119Alaska
10Baranof Island4,065Alaska
11Long Island3,629New York
12Revillagigedo Island2,965Alaska
13Kupreanof Island2,813Alaska
14Unalaska Island2,722Alaska
15Nelson Island2,183Alaska
16Kuiu Island1,962Alaska
17Maui1,883Hawaii
18Afognak1,809Alaska
19Umnak1,793Alaska
20Oahu1,545Hawaii
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