Alaska’s geography falls into clear physical regions laid out roughly in bands from north to south: the flat Arctic Coastal Plain of the North Slope, the Brooks Range, the Interior basins of the Yukon and Kuskokwim rivers, the low Bering Sea coast, and the Pacific Mountain System in the south, which takes in the Alaska Range, the Chugach, Wrangell and Saint Elias mountains, the Southeast Panhandle and the volcanic Alaska Peninsula and Aleutian Islands. The highest point is Denali in the Alaska Range at 6,190 m (20,310 ft), the highest summit in North America; the lowest is sea level along about 55,000 km (34,000 mi) of tidal shoreline. At 1,717,856 km² (663,268 sq mi), Alaska is more than twice the size of Texas, holds over 409,000 natural lakes of at least one hectare and has somewhere between about 41,000 and 75,000 km² of glacier ice, depending on the source. The longest river is the Yukon, 3,190 km from British Columbia to the Bering Sea, and the largest lake is Iliamna Lake at about 2,600 km².
The Arctic Coastal Plain: Utqiaġvik, Prudhoe Bay and the North Slope
North of the Brooks Range the land drops to a treeless, almost flat plain running down to the Beaufort and Chukchi seas. Its surface is tundra over permafrost, dotted with shallow thaw lakes; statewide, marsh and wetland permafrost cover about 487,700 km², mostly in the northern and western flatlands. The climate is Arctic tundra (Köppen ET): even in July the average low at Utqiaġvik, formerly Barrow, is about 1 °C, and most places get under 25 cm of precipitation a year. Utqiaġvik, with 4,927 people in 2020, is the northernmost town in the United States, and the Iñupiat have lived there for more than 1,500 years.
Beneath the plain lies the Prudhoe Bay Oil Field, the largest in North America, covering 86,418 hectares and originally holding about 25 billion barrels. It sits between the National Petroleum Reserve–Alaska to the west, about 9.3 million hectares, and the Arctic National Wildlife Refuge to the east, at about 78,050 km² the largest national wildlife refuge in the country. A spot inside the petroleum reserve, about 190 km from any town or village, is the point in the United States most remote from permanent habitation.
The Brooks Range: Mount Isto, Atigun Pass and Gates of the Arctic
The Brooks Range runs about 1,100 km (700 mi) across northern Alaska into Canada’s Yukon. In the United States it counts as a subrange of the Rocky Mountains, and it forms the divide between rivers flowing to the Arctic Ocean and those flowing to the Yukon and the Bering Sea. Its highest summit is Mount Isto at 2,736 m (8,976 ft), with Mount Hubley second and Mount Chamberlin, long thought to be the highest until a 2014 survey, now third. The name honours Alfred Hulse Brooks, the US Geological Survey’s chief geologist in Alaska from 1903 to 1924.
The range is almost empty: its only settlements are Anaktuvuk Pass, Arctic Village and a few hamlets such as Coldfoot and Wiseman. The one road across it, the Dalton Highway, crosses Atigun Pass at about 1,444 m (4,739 ft) beside the Trans-Alaska Pipeline. Most of the mountains lie inside Gates of the Arctic National Park, the Noatak National Preserve and the Arctic Refuge. In the western De Long Mountains, the Red Dog mine is the world’s largest producer of zinc.
The Interior Basins: Yukon, Tanana and Kuskokwim Valleys
South of the Brooks Range, the Interior is a region of rolling uplands and wide river flats under boreal spruce forest. The southern mountains shelter it from the sea, so it is dry, often receiving less than 25 cm of precipitation annually, and it has the widest temperature range in the state. Fairbanks, with 32,515 people in 2020, can pass 30 °C in summer and fall below −51 °C in winter. Both state records were set here: 38 °C at Fort Yukon on 27 June 1915 and −62 °C at Prospect Creek on 23 January 1971.
Three rivers drain the region. The Yukon crosses the whole width of Alaska from Canada; its basin covers about 854,700 km², and it was the main route of the 1896–1903 Klondike Gold Rush. Its tributary the Tanana, 940 km long, flows past Fairbanks along the foot of the Alaska Range. The Kuskokwim runs 1,130 km to Kuskokwim Bay and is the longest river system entirely within one US state, used by boats in summer and as an ice road in winter.
Bering Sea Lowlands: the Seward Peninsula and the Yukon–Kuskokwim Delta
Where those rivers meet the west coast, the land flattens into the Yukon–Kuskokwim Delta, about 129,500 km² and one of the largest deltas in the world, comparable in size to Louisiana. It is almost all tundra and ponds, protected in the Yukon Delta National Wildlife Refuge. About 25,000 people live there, around 85% of them Yup’ik and Athabascan, with Bethel as the hub; with virtually no roads, travel is by bush plane, riverboat or snowmachine.
Farther north, the Seward Peninsula projects about 320 km into the Bering Sea. Its tip, Cape Prince of Wales, is the westernmost mainland point of the Americas, 82 km across the Bering Strait from Russia’s Cape Dezhnev. The peninsula is a remnant of Beringia, the Ice Age land bridge between Siberia and Alaska, preserved in the Bering Land Bridge National Preserve. The coast of Kotzebue Sound is dry enough to count as desert, with parts seeing less than 25 cm a year, while places between Dillingham and Bethel average about 250 cm.
The Alaska Range and Denali
The inland arc of the Pacific Mountain System is the Alaska Range, about 970 km long, curving from Lake Clark east to the White River in Yukon. It blocks moist air from the Gulf of Alaska, so it catches heavy snow that feeds glaciers such as the Muldrow, Ruth and Kahiltna, and the Denali Fault along its southern edge causes many of the region’s major earthquakes.
Denali, measured at 6,190 m (20,310 ft) by the US Geological Survey in 2015, is a granitic pluton lifted as the Pacific Plate dives beneath the North American Plate. It rises about 5,500 m above the surrounding lowlands, and its prominence of 6,144 m is third in the world after Everest and Aconcagua. The State of Alaska adopted the Koyukon name Denali in 1975. The federal government used it from 2015 but restored Mount McKinley in January 2025. The first verified ascent came on 7 June 1913. The peak is the centrepiece of Denali National Park and Preserve.
Southcentral Alaska: Chugach Mountains, Cook Inlet and Turnagain Arm
Between the Alaska Range and the Gulf of Alaska lies Southcentral, the most populated region. Anchorage, with 291,247 people in 2020, sits at the head of Cook Inlet between Knik Arm and Turnagain Arm, and its metro area, including Palmer and Wasilla, held 398,328 of the state’s 733,391 people. The Chugach Mountains wall in the coast for about 400 km, rising to Mount Marcus Baker at 3,991 m (13,094 ft); facing the Gulf of Alaska, they get more snow than anywhere else in the world, an average of over 1,500 cm a year. Turnagain Arm has a tidal range of more than 10.7 m (35 ft).
This coast was reshaped by the Good Friday earthquake of 27 March 1964, a magnitude 9.2 shock and the most powerful recorded in North America. It killed about 139 people, raised land near Kodiak by up to 9 m and dropped ground around Girdwood and Portage by up to 2.4 m.
Wrangell–Saint Elias Mountains and the Southeast Panhandle
East of the Chugach rise the highest coastal mountains on the continent. The volcanic Wrangell Mountains include Mount Blackburn at 4,996 m (16,390 ft) and Mount Sanford at 4,949 m, the second- and third-highest volcanoes in the United States. On the Yukon border, Mount Saint Elias reaches 5,489 m (18,008 ft) only about 18 km from the Pacific, the second-highest peak in both the US and Canada. Below it spreads the Malaspina Glacier, between Icy Bay and Yakutat Bay, the largest piedmont glacier in the world at about 3,900 km². Nearby, the Hubbard Glacier has been advancing for about a century, briefly damming Russell Fjord in 1986.
South of Yakutat begins the Panhandle: mainland and the islands of the Alexander Archipelago between the Coast Mountains and the Pacific, a land of fjords and temperate rainforest. Ketchikan averages over 380 cm of precipitation a year, and most of the region lies in the Tongass National Forest, at about 68,000 km² the largest national forest in the US. The capital, Juneau, sits below the 3,900 km² Juneau Icefield, source of the Mendenhall and Taku glaciers, and no road links it to the rest of North America. To the west, the ice that filled Glacier Bay in 1794 had retreated about 77 km by 1879.
The Alaska Peninsula and Aleutian Islands: from Novarupta to Attu
The mountain system ends in a volcanic arm reaching south-west. On the Alaska Peninsula, Iliamna Lake, 124 km long and up to 301 m deep, drains into Bristol Bay, home of the world’s largest sockeye salmon fishery. In today’s Katmai National Park, the 1912 eruption of Novarupta was the largest of the 20th century. It threw out 13 to 15 km³ of ash, about 30 times the 1980 Mount St Helens eruption, and created the Valley of Ten Thousand Smokes.
Beyond, the Aleutian Islands stretch about 1,900 km towards Kamchatka between the Bering Sea and the Pacific: 14 large and 55 smaller islands with 57 volcanoes, the northern edge of the Ring of Fire. The highest is Shishaldin on Unimak Island, 2,857 m (9,373 ft).
Because the chain crosses the 180° meridian, Alaska is the northernmost, westernmost and, by longitude, easternmost US state; the International Date Line bends west of Attu so the whole state keeps one calendar day. How this land became American is told in our guide to the Alaska Purchase of 1867, and the river that ties the Interior together has its own Yukon River guide.