President Donald Trump recently said the U.S. must acquire Greenland (not lease it), arguing the Arctic territory lacks defenses and warning that Russia or China would move in if Washington does not act.

In retrospect, the United States has acquired several territories over time, and its history presents a mix of acquisition methods, including purchase, cession, and occupation. 

Leaving the world to wonder what their trump card would be in acquiring Denmark-controlled Greenland. 

TL;DR 

• U.S. territorial expansion shifted from 19th-century land purchases to strategic island cessions, leading to its status as a world power. 
• Major acquisitions like Louisiana and Alaska reshaped America at low cost amid debates over indigenous rights.

The data used in this explainer comes from BallotPedia.

United States Territorial Acquisition 

Based on these trends, the United States mainly gained territory through three methods: buying, occupying, and ceding land. 

Over time, the focus shifted from expanding within the continent to acquiring overseas territories.

In the early 1800s, purchases were the primary method, like when the U.S. bought the Louisiana Territory from France in 1803 and Alaska from Russia in 1867. 

These deals helped the U.S. quickly expand its land through negotiations and payments.

After wars or treaties, the U.S. sometimes gained land through cession. 

Notable examples include the Mexican Cession in 1848 and the Marianas Islands in 1947, in which control was transferred from defeated countries or independent nations to the U.S.

• Alaska was bought in 1867 for $7.2 million, covering 591,000 square miles. Thought to be a “barren land” at first, it turned out to be valuable for its resources and strategic location.
• Hawaii was annexed in 1898 and cost nothing. It covered 6,450 square miles and gave the U.S. a key Pacific naval base, strengthening its military power in Asia.

These land expansions came at a high human cost, driven by migration and displacement. 

Indigenous peoples were displaced across millions of square miles, and policies of removal and assimilation changed cultures and populations forever.

The Greenland Conversation

Recall that in the mid-1800s, the U.S. took control of small Pacific islands like Baker and Wake Islands. 

These claims were mainly strategic and didn’t require much diplomacy because these islands weren’t populated, unlike Greenland, which has a population and is self-governing. 

Claiming Greenland unilaterally would violate international law in a world where decolonization shapes interactions. 

The U.S. also gained territories such as Hawaii and Puerto Rico through war or mandates. 

These acquisitions often ran counter to local wishes. This is different from Greenland, where Denmark’s NATO membership makes the use of force impossible, despite U.S. strategic interests.

Today, the idea of pursuing Greenland raises questions about sovereignty, the environment, and alliances as countries reassess their roles in the world.

Potential ‘hard ways’ Trump could try to take Greenland?

Trump’s soft approach might offer Greenlanders between $10,000 and $100,000 each, totaling up to $5.6 billion, to encourage them to hold a referendum on leaving Denmark. 

This would be similar to past U.S. financial moves, such as the 1917 purchase of the Virgin Islands, but it would face about 85% local opposition and criticism from the EU.

However, Denmark says Greenland isn’t for sale…

And, there are no modern examples of countries being forced to sell territory.

In contrast, a hard approach would be a military takeover using the Pituffik Space Base, which has 650 U.S. personnel, to take over control with little resistance from Denmark. 

This would be similar to 19th-century land cessions after wars, but it would violate NATO rules and damage alliances.

Another option is a Compact of Free Association, like agreements the U.S. has with Pacific nations. This would involve helping Greenland become independent and giving the U.S. control over defense, while focusing on diplomacy rather than coercion.

ELI5

The United States became a world power through land expansions and the occupation of strategic islands, especially during the 19th century. 

To get these territories, the U.S. either pays in money, claims ownership, then occupies them, or makes another country sign them over. 

Some major acquisitions cost money but were cheap, like Louisiana at $15 million and Alaska at $7.2 million, significantly benefiting America. 

Yet, these deals caused issues over the rights of the indigenous people.

Presently, the U.S. has declared interest in acquiring Greenland. Achieving this could mirror past approaches, with the hard way option in play, such as using military force, which conflicts with modern International laws. 

Sources: 

BallotPedia | National Geographic | Library of Congress | Al Jazeera