In 1868, Secretary of State William Seward went on a territory-shopping spree. A year earlier, Seward had negotiated the purchase of Alaska from Russia for $7.2 million. If Seward’s acquisition of Alaska hadn’t been politically branded as a “folly,” he may have gotten his wish to add Greenland (and Iceland) to the expanding United States.

America’s longstanding interest in Greenland and other northern territories—including Canada—was about expanding U.S. control over North America and the increasingly important arctic region, according to Ron Doel, a historian at Florida State University.

“What’s interesting is that so much of U.S. ideology usually involved looking West,” says Doel. “But every now and again, it was, ‘Let’s look North.’ And Greenland fits in that along with the purchase of Alaska.”

If Alaska was considered terra incognita to most Americans in the mid-19th century, even less was known about Greenland. That’s why Seward ordered a detailed survey in 1867 of the ice-capped island ruled by Denmark. The report, published in 1868, portrayed Greenland as a land of abundance.

“Greenland has in vast quantities whale, walrus, seal and shark, cod, salmon, salmon-trout and herring; foxes, wolf, reindeer, bear, a myriad of birds,” wrote Seward in a summary. “Good coal is found on the western coast at various points, extending far north, most cheaply mined and close to good harbors.”

As he had done with Alaska, Seward promoted Greenland as a land of nearly inexhaustible natural resources—especially coal, but also whale blubber and a mineral called criolite—that would empower the United States to “command the commerce of the world.”

By 1868, however, the purchase of Alaska was being actively mocked in newspapers as “Seward’s Folly,” “Seward’s Ice Box” and “Andrew Johnson’s Polar Bear Garden.” (It would still be decades before the Yukon Gold Rush made Alaska a valuable asset.) Congress and the American public had no appetite for more frozen territories, so Seward’s proposed purchase of Greenland fizzled.

In the early 20th century, another scheme was in the works for the United States to get its hands on Greenland. This proposal, engineered by the U.S. ambassador to Denmark, wasn’t for America to buy Greenland, but to acquire it through an elaborate three-way trade.

On September 20, 1910, Ambassador Maurice Egan sent a letter to the U.S. State Department outlining the land swap. At the time, Denmark was still stinging from the loss of a valuable territory called Schleswig-Holstein situated between Denmark and Germany. In talks with Danish leaders, Egan figured out a way by which Denmark could potentially regain the Schleswig-Holstein region, which it had lost to a German confederation in 1864.

Here’s how the swap would have worked: 1.) Denmark cedes Greenland to the United States. 2.) In exchange for Greenland, the U.S. gives Denmark a cluster of islands in the Philippines. 3.) Denmark turns around and gives the Philippine islands to Germany (which was seeking more influence in the East). 4.) Germany, in return, gives Schleswig-Holstein back to Denmark.

Even Egan called his plan an “audacious suggestion” and apparently the U.S. government agreed. No action was taken on the Greenland swap, although it may have paved the way for the U.S. to buy the Virgin Islands from Denmark in 1917.

The closest the United States came to making a legitimate offer to buy Greenland from Denmark was in 1946, immediately after World War II. During the war, more than 10,000 Allied aircraft landed on Greenland to refuel for bombing runs in Germany.

“The Pentagon thought of Greenland as the world’s largest stationary aircraft carrier,” says Doel, co-editor of Exploring Greenland: Cold War Science and Technology on Ice. “Planes weren’t flying all the way across the Atlantic. Having places like Greenland and Iceland became crucial.”

At the outset of World War II, Denmark declared its neutrality, but Germany invaded Denmark in 1940 and placed it under Nazi occupation. Since Denmark still ruled Greenland, there was great concern in the U.S. that Germany would invade Greenland too, giving the Nazis a North American base of operations.

In 1941, the U.S. Secretary of State signed the “Defense of Greenland” treaty with Denmark’s ambassador to the United States in Washington, D.C. The pact made America responsible for Greenland’s defense during the war, and gave the U.S. military the right to build any necessary facilities to land its planes.

Greenland proved such a strategic asset during World War II that there was great interest at the top levels of government in buying the island from Denmark. In 1946, a State Department envoy to Europe named William Trimble proposed paying Denmark $100 million in gold in exchange for all of Greenland.

The cash offer was met with shock and dismay in Denmark.

“The Danes were rather horrified that the U.S. thought it could gain a territory by putting that kind of a monetary value on it, and that Denmark would be willing to part with it,” says Doel.

Gustav Rasmussen, the Danish Foreign Minister told the U.S. ambassador to Denmark, “While we owe much to America, I do not feel that we owe them the whole island of Greenland.”

The Cold War between the U.S. and the Soviet Union placed Greenland at the geographic midpoint between the nuclear powers.

“If there is a third war,” declared General H.H. “Hap” Arnold, “its strategic center will be the north pole.”

Instead of leaving Greenland after the end of World War II, the U.S. signed a new treaty with Denmark in 1951 that gave the American military even more latitude to use Greenland as its base of arctic operations.

Under a secret project codenamed “Blue Jay,” the U.S. built a massive air base on the Northwest coast of Greenland. The construction of the Thule Air Base between 1951 and 1953 has been compared to the Panama Canal in its difficulty and complexity. The project required 12,000 workers and shipments of 300,000 tons of cargo.

At the peak of the Cold War, the Thule Air Base in Greenland housed 10,000 American troops. The base gave the U.S. a rapid response to Soviet nuclear threats, since American bombers taking off from Thule could reach targets like Leningrad and Moscow in a matter of hours.

The U.S. even experimented with the construction of military installations underneath Greenland’s ice sheet, starting with an outpost 150 miles from Thule Air Base called Camp Century.

“Camp Century was a nuclear-powered city under the ice with a bowling alley, religious chapels, a mess hall and a library,” says Noel.

Camp Century was a proof-of-concept for an even more ambitious scheme called “Project Earthworm.” For that project, the U.S. military wanted to build a network of railroad tracks under Greenland’s ice to shuttle around nuclear missiles capable of reaching the Soviet mainland. Project Earthworm was never completed.

According to a memo addressed to President Dwight Eisenhower from his Secretary of Defense, the Pentagon was still very interested in buying Greenland as late as 1955, but no official offer was made.

Denmark granted Greenland “home rule” in 1979, meaning that Greenland operates as a sovereign nation with Denmark still involved in its defense and foreign affairs. The U.S. retains a military presence in Greenland, although the Thule Air Base was transferred to the U.S. Space Force in 2020 and is now called the Pituffik Space Base.