At the National Constitution Center, we value civil dialogue, which empowers students to speak about constitutional and historical topics in ways that remain civil, respectful, and reflective. As you prepare to discuss these topics in your classroom, we encourage you to establish norms such as:
- Stay calm
- Listen patiently
- Listen actively
- Don’t speak twice until everybody has spoken once
You can find more support for establishing norms and civil dialogue practices in our Civil Dialogue Toolkit.
Media Asset
National Constitution Center's Constitution Daily Blog – A brief history of the annexation of foreign territories by the United States, by Scott Bomboy
Big Constitutional Questions
- Can the United States acquire foreign territories, such as Greenland?
Headline Story
Recent comments by President Donald Trump about negotiating to acquire Greenland have generated new interest in an old constitutional question: how and under what authority the United States may acquire new territory. Although the Constitution explains how new states are admitted and how territories are governed, it does not directly describe how land can be acquired. Throughout U.S. history, the country has gained territory through treaties, congressional resolutions, purchases, and war.
The question of territorial acquisition was first addressed in the Articles of Confederation. The Articles invited Canada to join the Union (which never happened), and the Northwest Ordinance created rules for governing new lands. Under the United States Constitution, Congress gained authority for admitting new states under Article IV, Section 3, and in 1791 and 1792, respectively, Vermont and Kentucky joined the Union through this framework. Later acquisitions raised constitutional debates, especially the Louisiana Purchase, where President Jefferson relied on treaty powers despite uncertainty about constitutional authority. The Supreme Court later decided in American Insurance Co v. Canter (1828), “The Constitution confers absolutely on the government of the Union, the powers of making war, and of making treaties; consequently, that government possesses the power of acquiring territory, either by conquest or by treaty”.
Subsequent expansion followed multiple pathways. The annexation of Texas in 1845 and Hawaii in 1898 occurred through joint resolutions of Congress, a method that generated significant controversy. Other territory was gained through treaties following war, including the Mexican Cession under the Treaty of Guadalupe Hidalgo in 1848 and overseas territories acquired from Spain in the Treaty of Paris in 1898. The United States also purchased Alaska in 1867. The last major permanent acquisition occurred in 1917 with the purchase of the Danish West Indies, now the U.S. Virgin Islands.
Debates about territorial expansion have consistently revealed tensions between constitutional interpretation, political power, and national interest. President Trump’s recent proposal shows that questions about acquiring territory remain relevant today, connecting modern policy discussions to long-standing constitutional and historical debates.
Amendment / Clause Focus
- Article IV, Section 3 – outlines the process of admitting a new state
- Article II, Section 2 – executive power to make treaties
Scholar Perspectives
|
Scholar |
Key Ideas & Quote |
Why It Matters |
|
Eric Biber and Thomas B. Colby |
“New states have generally been admitted after a period of territorial government, during which Congress and the President have broad authority pursuant to the Property Clause, also in Article IV, Section 3. An Act of Congress established the territorial government, often giving greater self-government (e.g., in the form of an elected territorial legislature) as the territory’s population increased over time.” |
When the United States gains new territory, it does not automatically become a state. There is usually a transition period in which Congress and the President establish a territorial government and gradually expand self-government as the population grows. |
|
John O. McGinnis and Peter M. Shane |
“In general, the weight of practice has been to confine the Senate’s authority to that of disapproval or approval, with approval including the power to attach conditions or reservations to the treaty.” |
This quote is significant because it highlights the distribution of power within the U.S. government, particularly in matters of international agreements. It clarifies that while the President negotiates treaties, the Senate holds the authority to approve or reject them and even propose conditions. Consequently, major decisions, such as acquiring territory, forming alliances, or establishing trade agreements, are not the sole responsibility of a single individual. |
|
John O. McGinnis |
“The results of an originalist reading of these Clauses would at times favor the President, but at other times disfavor him, but they would more generally promote accountability.” |
Constitutional interpretation significantly influences the actual functioning of government. The passage contends that interpreting the Constitution based on its original meaning can enhance accountability by clearly defining the authority of various branches, such as the President, Congress, or the courts, rather than relying on evolving interpretations that may lead to inconsistent decision-making. |
|
Peter M. Shane |
“Article II of the U.S. Constitution is plainly critical to establishing two fundamental institutional relationships: the President's relationship with Congress and the President's relationship to the remainder of the executive establishment.” |
Article II of the Constitution is not merely a description of the President’s responsibilities. It establishes the framework for power distribution and balance within the federal government. By delineating the President’s relationship with Congress and the executive branch, the Constitution lays the groundwork for decision-making processes, encompassing significant matters such as foreign policy, treaties, and territorial issues. |
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Think, Talk, Create
Student Questions
- Where does the Constitution grant powers related to territorial acquisition? How do checks and balances play a role in this process?
- What are the different ways the United States has acquired territories since 1776?
- How have global events shaped decisions related to acquiring new territories throughout American history, and what has the impact been on the United States?
Student Choice Options
- Create a political cartoon that represents the history of territorial acquisition of foreign nations by the United States.
- Select an acquired territory mentioned in the blog post. Conduct research about that territorial acquisition, as well as the current conversation about Greenland. Write a short comparative essay or create an infographic that responds to the following questions:
- In each case, what was the historical context surrounding the acquisition?
- What constitutional justification was used?
- What unresolved questions remain?
- Using the Consensogram protocol, have student assess their level of agreement with the following statement: The United States has the constitutional authority to acquire Greenland. As students share their responses and engage in dialogue, they should be sure to:
- Cite at least one historical precedent
- Reference at least one constitutional clause or U.S. Supreme Court Case
- Address the perspective of Greenland and its current context
Beyond the Headlines
- Interactive Constitution:
- American Insurance Co. V. Canter (1823)
- “The Constitution confers absolutely on the government of the Union, the powers of making war, and of making treaties; consequently, that government possesses the power of acquiring territory, either by conquest or by treaty,” - Chief Justice John Marshall
