Isle Royale National Park is a national park in the United States. It includes Isle Royale and more than 400 small nearby islands, along with the surrounding waters of Lake Superior in Michigan.

Isle Royale is 45 miles (72 kilometers) long and 9 miles (14 kilometers) wide. It covers an area of 206.73 square miles (535.4 square kilometers), making it the fifth-largest lake island in the world. It is the largest natural island in Lake Superior, the second-largest island in the Great Lakes (after Manitoulin Island), the third-largest island in the contiguous United States (after Long Island and Padre Island), and the 33rd-largest island in the United States.

Isle Royale National Park was created on April 3, 1940. In 1976, it was protected from development as a wilderness area. In 1980, it became a UNESCO International Biosphere Reserve. In 2019, the Minong Traditional Cultural Property was added to the National Register of Historic Places. The park covers 894 square miles (2,320 square kilometers), with 209 square miles (540 square kilometers) of land and 685 square miles (1,770 square kilometers) of surrounding water.

The park's northern edge is next to the Canadian Lake Superior National Marine Conservation Area, which is located along the border between the United States and Canada. In 2021, the park had 25,894 visitors. This makes it the seventh least visited national park in the United States.

Geography

In 1875, Isle Royale was separated from Keweenaw County to form its own county, called Isle Royale County. In 1897, the county was removed, and the island was added back into Keweenaw County. The highest point on the island is Mount Desor, which is 1,394 feet (425 meters) tall, or about 800 feet (240 meters) above the level of the lake.

Isle Royale, the largest island in Lake Superior, is more than 45 miles (72 kilometers) long and 9 miles (14 kilometers) wide at its widest point. The park includes Isle Royale itself, about 400 smaller islands, and any underwater areas within 4.5 miles (7.2 kilometers) of the surrounding islands (16USC408g).

Isle Royale is located about 15 miles (24 kilometers) from the shore of Ontario, Canada, near Thunder Bay, and next to Minnesota, near Grand Portage in Cook County. It is 56 miles (90 kilometers) from the Michigan shore on the Keweenaw Peninsula, which is part of the Upper Peninsula. There are no roads on the island, and wheeled vehicles or devices, except wheelchairs, are not allowed. Rock Harbor provides wheeled carts to move personal items from the marina to cabins and the hotel. The National Park Service uses tractors and utility terrain vehicles to transport items in developed areas at Ozaagaateng, Rock Harbor, and Mott Island.

The topsoil on the island is often thin, which helps trees with horizontal roots, such as balsam fir, white spruce, and black spruce, grow better.

Siskiwit Lake is the largest lake on the island. It has cold, clear water and is low in nutrients. Siskiwit Lake includes several islands, with Ryan Island being the largest. Other lakes on the island are:

• Chicken Bone Lake
• Lake Desor
• Feldtmann Lake
• Intermediate Lake (Isle Royale)
• Lake Ritchie
• Sargent Lake
• Hatchet Lake

Climate

Isle Royale National Park has a type of climate called "Humid continental" with mild summers, classified as Dfb in the Köppen system. The United States Department of Agriculture states that the park’s Plant Hardiness zone is 4b at an elevation of 1,178 feet (359 meters), where the average annual extreme minimum temperature is -24.2 °F (-31.2 °C).

There is no weather station within the park. Instead, the PRISM Climate Group, a project of Oregon State University, uses data from nearby areas to estimate the island’s climate.

History

The island was a shared hunting area for Native people from Minnesota and Ontario. A canoe trip of thirteen miles is needed to reach the island’s western end from the mainland.

Large amounts of copper tools and objects found in Native mounds and homes, some from as early as 3000 B.C., were likely mined on Isle Royale and the nearby Keweenaw Peninsula. The island has many pits and trenches up to 65 feet (20 meters) deep, made by these early people, mostly in the McCargoe Cove area. Testing of wood found in copper artifact sockets shows these items are at least 6,500 years old.

In Prehistoric Copper Mining in the Lake Superior Region, Drier and Du Temple estimated that over 750,000 tons of copper were mined in the area. However, David Johnson and Susan Martin argue that their estimate was based on incorrect assumptions. A Jesuit missionary named Dablon wrote in 1669–70 about “an island called Menong, celebrated for its copper.” Menong, or Minong, was the Native name for the island, and it is the source of Minong Ridge. Serious mining began in 1843 after the Chippewa people gave up their claims to the island, using many of the original Native pits. This activity stopped by 1855, as no valuable copper was found. The Minong Mine and Island Mine were short-lived projects from 1873 to 1881.

Isle Royale was given to the United States in the 1783 treaty with Great Britain (previously part of a disputed Indian Reserve). The British kept control until after the War of 1812, and the Ojibwa people considered the island their land. The Ojibwa ceded the island to the U.S. in the 1842 Treaty of La Pointe, though the Grand Portage Band did not know the island was not British territory. After the 1842 Webster–Ashburton Treaty clarified the situation, the Ojibwa reaffirmed the 1842 Treaty of La Pointe in the 1844 Isle Royale Agreement, with the Grand Portage Band signing as an addendum.

In the mid-1840s, a report by Douglass Houghton, Michigan’s first state geologist, led to a copper boom in the state. The first modern copper mines opened on the island. Evidence of earlier mining efforts was visible, including stone hammers, copper objects, and partially worked copper in rock. Ancient pits and trenches helped locate copper deposits mined in the 19th century. The island’s distance from the mainland and small copper veins caused most 19th-century mines to fail quickly. Logging and mining in the late 1800s led to widespread deforestation. When Isle Royale became a national park in 1940, logging and other harmful activities stopped, and forests began to regrow.

The island once had several fisheries for lake trout and whitefish, as well as a few resorts. The fishing industry has declined, but Edisen Fishery still operates. Today, no permanent residents live on the island. Small communities of Scandinavian fishermen were removed by the U.S. National Park Service when the island became a national park in the 1940s. About 12 families still have lifetime leases for cabins on the island and claim it as their heritage. Some descendants of fishermen continue to fish commercially in Isle Royale waters.

Because many small islands surround Isle Royale, lighthouses once guided ships through the area. These lighthouses were located on Passage Island, Rock Harbor, Rock of Ages, and Menagerie Island. The western tip of the island has several shipwrecks popular with scuba divers, including the SS America. The NPS Submerged Resources Center mapped the 10 most famous shipwrecks in the park and published Shipwrecks of Isle Royale National Park; The Archeological Survey, which describes the area’s maritime history. The region’s harsh weather, underwater terrain, central location on historic shipping routes, and cold, fresh water have preserved many shipwrecks well.

In January 2019, the entire island chain was added to the National Register of Historic Places by the federal government. It is listed as “the Minong Traditional Cultural Property.”

In 1845, an Ojibwe woman named Angelique and her voyageur husband Charles Mott were left on Isle Royale by Cyrus Mendenhall and the Lake Superior Copper Company. They were hired to scout for copper. Angelique found a large copper ore deposit. She and her husband were asked to stay and guard it until a barge could retrieve it, expected within three months. They were dropped off in July and remained stranded until the next spring. They had limited supplies: a half-barrel of flour, six pounds of butter, and some beans. A supply boat was promised but never arrived.

Angelique’s story was recorded in a footnote in the first edition of The Honorable Peter White by Ralph D. Williams in 1907. Her story was removed from later editions, making it the only surviving written account. Humans have not typically lived on Isle Royale year-round. For about 3,000 years, Native Americans used the island for copper and fishing, visiting mainly in the summer. Nineteenth-century Americans also visited seasonally.

Natural history

Isle Royale National Park has many different types of habitats. The main one is a boreal forest, similar to those found in Ontario and Minnesota. Some high areas have "balds," which are places with exposed rocks, a few small trees, blueberry bushes, and hardy grasses. There are also marshes, often created by beavers, and several lakes with forested or marshy edges. The climate in lowland areas is strongly affected by the cold water of Lake Superior.

According to the A. W. Kuchler U.S. Potential Natural Vegetation Types, the park has a Great Lakes Spruce/Fir (93) potential vegetation type and a Northern Conifer Forest (22) potential vegetation form.

The main plant habitats on Isle Royale are in the Laurentian Mixed Forest Province. This area is a transition zone between the true boreal forest to the north and the Big Woods to the south, showing features of both. It includes areas with both broadleaf and conifer trees, as well as wetlands like bogs and swamps.

Conifer trees found here include jack pines, black and white spruces, balsam firs, and eastern redcedars. Deciduous trees include quaking aspens, red oaks, paper birches, American mountain ash, red and sugar maples, and mountain maples. Over 600 species of flowering plants grow here, such as wild sarsaparilla, marsh-marigold, wood lily, and prickly wild rose.

Isle Royale is famous for its wolf and moose populations, which scientists study to understand predator-prey relationships in a closed environment. Moose and wolves have a cycle: when moose numbers increase, so do wolves. Eventually, wolves may kill too many moose and starve, reducing their reproduction. This happens partly because the park has only about one-third of the mainland’s mammal species due to its remote location. The area is unique because it is the only place where wolves and moose coexist without bears.

Other mammals include red foxes, beavers, and red squirrels. Some foxes are used to humans and can be seen near campgrounds. Wolves, however, avoid humans and rarely interact with them. In 2024, many wolf sightings were reported near Rock Harbor. Other animals include ermine near docks, mink along lakeshores, muskrats at beaver ponds, and several bat species. Reptiles include eastern garter snakes, painted turtles, and northern redbelly snakes. Six frog species and three salamander species also live on the island.

Historically, moose and wolves did not live on Isle Royale. Before becoming a national park, the main large mammals were Canada lynx and boreal woodland caribou. These animals were present for about 3,500 years but were removed by human actions like hunting, trapping, and logging. The last caribou was seen in 1925, and lynx disappeared by the 1930s, though some occasionally crossed the ice from Ontario. Coyotes were also on the island until wolves arrived in the 1950s. In 2018, four wolves were brought from Minnesota after debate about whether this was a natural process.

Moose likely arrived on Isle Royale between 1905 and 1912. Early theories suggested they swam or crossed ice from the mainland, but genetic and cultural evidence now suggests humans transported them to create a hunting preserve. Moose on the island are genetically closer to those in northwestern Minnesota than nearby areas, supporting this theory. The Washington Harbor Club, a group of wealthy businessmen, owned land on the island and had the means to move moose from Minnesota.

Wolf and moose populations on the island vary greatly each year. In 2006–2007, there were 385 moose and 21 wolves in three packs. By 2008, there were about 650 moose and 23 wolves. However, reduced winter ice limited wolf migration from the mainland. By 2016, inbreeding had reduced the wolf population to two individuals, and moose numbers rose to about 1,600. By 2017, only one wolf remained.

In 2016, the National Park Service proposed bringing more wolves to the island. From 2018 to 2019, 19 wolves were relocated from Minnesota, Michigan, and Ontario. By April 2020, about 14 wolves were estimated to be on the island.

The island’s landscape is mostly ridges running southwest to northeast. Greenstone Ridge, the main ridge, is over 1,000 feet high in some areas. Greenstone, a type of rock with rounded chlorastrolite stones, is found near lakes.

Two main rock types are present: the Portage Lake Volcanics and the Copper Harbor Conglomerate, both from the Precambrian era. The volcanics are layers of basalt, with over 100 flows totaling at least 10,000 feet. The conglomerate, found on the island’s southwest side, is sedimentary rock formed from volcanic material in Minnesota. Glaciers shaped the island’s ridges and valleys, with glacial striations showing westward glacier movement. Drumlins are found near Siskiwit Lake.

Recent studies by the U.S. Geological Survey show differences between unmineralized basalt and copper-rich rock on the island.

Recreation

Recreational activities on Isle Royale include hiking, backpacking, fishing, boating, canoeing, kayaking, and observing nature. Wheeled vehicles are not allowed on the island, but wheelchairs are permitted.

The island has about 170 miles (270 kilometers) of hiking trails for day hikes or longer trips, such as a two-week hike around the island. Some trails are very difficult, with steep hills. The Greenstone Ridge is a high area in the center of the island and includes the longest trail, the Greenstone Ridge Trail, which stretches 40 miles (64 kilometers) from one end of the island to the other. This trail is usually completed in 4 or 5 days. A boat shuttle can help hikers return to their starting point. The trail leads to Mount Desor, the island’s highest point at 1,394 feet (425 meters), and passes through forests, glacial lakes, swamps, bogs, and scenic shorelines.

In total, there are 165 miles (266 kilometers) of hiking trails. There are also canoe and kayak routes, many of which require carrying boats between waterways, along coastal bays and inland lakes.

The park has two developed areas:

• Ozaagaateng (formerly Windigo), at the southwest end of the island (where ferries from Minnesota arrive). This area has a campstore, showers, campsites, rustic camper cabins, and a boat dock.
• Rock Harbor, on the south side of the northeast end (where ferries from Michigan arrive). This area has a campstore, showers, a restaurant, a lodge, campsites, and a boat dock. The only non-camping sleeping options are the lodge at Rock Harbor and the camper cabins at Ozaagaateng.

The park has 36 designated wilderness campgrounds. Some are only reachable by hiking trails or by canoe/kayak on island lakes. Others are only accessible by private boat. Campsites vary in size but often include three-sided wood shelters (with the fourth side having a screen) and areas for small tents. Some sites can accommodate groups of up to 10 people.

Campgrounds have pit toilets, picnic tables, and fire rings in specific areas. Campfires are not allowed at most campgrounds, so gas or alcohol stoves are recommended. Drinking and cooking water must be taken from local sources (Lake Superior and inland lakes) and filtered, treated, or boiled to avoid parasites. Hunting is not allowed, but fishing is permitted. Edible berries, such as blueberries and thimbleberries, can be picked along trails.

The park is accessible by ferries, floatplanes, and passenger ships during summer months from Houghton and Copper Harbor in Michigan and Grand Portage in Minnesota. Private boats also travel to the island from the coasts of Michigan, Minnesota, and Ontario. Isle Royale is popular with day-trippers in private boats, and day-trip ferry service is available from Copper Harbor and Grand Portage.

Isle Royale is the only American national park that closes completely in winter, from November 1 through April 15, due to extreme weather and for visitor safety. It is the least-visited national park in the contiguous United States because of its winter closure and location across Lake Superior. The average annual visitation from 2009 to 2018 was about 19,000, with 25,798 visitors in 2018. Only three remote Alaskan national parks—Lake Clark, Kobuk Valley, and Gates of the Arctic—have fewer visitors.

Scheduled ferry service operates from Grand Portage, Copper Harbor, and Houghton.

• Grand Portage ferries take 1½ hours to reach the island and stay for 4 hours, allowing time for hiking, guided programs, or picnics.
• Isle Royale Queen (from Copper Harbor) arrives at Rock Harbor in 3 to 3½ hours and stays for 3½ hours before returning.
• Sea Hunter offers round-trips and day trips to Ozaagaateng, including kayak and canoe transport. It is the fastest ferry, arriving in 1½ hours, and allows visitors to spend four hours on the island.
• Ranger III is a 165-foot (50-meter) ship that travels from Houghton to Rock Harbor in six hours. It carries passengers, canoes, kayaks, and small powerboats and makes two round trips weekly from June to mid-September.
• Voyageur II (from Grand Portage) crosses up to three times a week, overnighting at Rock Harbor and providing transportation between campgrounds. In fall, it also offers day-trip service to Ozaagaateng on weekends. It transports kayaks and canoes for visitors exploring the island.

Ferry services help hikers travel to different parts of the island, allowing them to hike one way and return by boat to Rock Harbor or Ozaagaateng. Some visitors land at Rock Harbor and leave from Ozaagaateng days later, or vice versa. Hikers often use the ferry to start a cross-island hike and return by boat from the opposite end.