American Imperialism, the First World War and the 1920s
Trace US expansion and intervention, entry into the First World War and the uneven boom and cultural conflicts of the 1920s. Use foreign-policy decisions and varied American experiences to explain change without treating growth or wartime mobilisation as universal benefit.
Section 2 · American Imperialism, the First World War and the 1920s
Exam scope and assessment notes
Cambridge lists AS Level US History since 1877 (8102) for centres in the United States of America only. It is a new qualification for first assessment in 2027 and replaces the US route through 9489; the last US 9489 assessment is November 2026. All historical analysis is original study material. Learners should verify details against the current official syllabus and prescribed class materials. Extended responses here are for formative practice only: StudyForA does not reproduce Cambridge questions, authenticate assessed work, apply official mark schemes or award Cambridge grades.
Before you begin
- Identify the date range and exact issue in the key question.
- Distinguish evidence, interpretation and judgement; compare groups and perspectives.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which approach best prepares for american imperialism, the first world war and the 1920s?
What you will learn
- What were the causes and consequences of US territorial expansion in the late-nineteenth and early-twentieth centuries?
- Why did the US enter the First World War and how did the war impact Americans?
- What were the causes and impacts of economic and cultural changes in the 1920s?
2.1 · Expansion and imperialism
Explain economic, cultural and nationalist motives: closing of the frontier, markets and resources, military and political aims, the Spanish–American War, and the ‘white man's burden’. Assess Theodore Roosevelt's Corollary to the Monroe Doctrine (Roosevelt Corollary), the Panama Canal and Great White Fleet, then Taft's Dollar Diplomacy and Wilson's Moral Diplomacy and interventions in Latin America and the Caribbean.
Compare pro- and anti-imperialist arguments and the changing status of territories, including the Insular Cases and Jones Act. Do not describe expansion as only a policy debate: include people living in affected territories and the power relationships involved.
2.2 · War entry and home-front change
Trace Wilson's initial desire to keep the US out, unrestricted submarine warfare and the Lusitania, anti-German sentiment, the Zimmermann Telegram and entry into war. Explain mobilisation through propaganda, rationing, conscription and civil-liberties restrictions such as the Espionage Act, Sedition Act and Schenck v. United States.
Compare women's roles, military segregation, African American, Hispanic American and Native American soldiers, the Great Migration, strikes and the National War Labor Board. Different groups experienced wartime opportunity and constraint in different ways.
2.3 · Boom, conflict and cultural change
Assess post-war growth, ‘Return to Normalcy’, low taxes, high tariffs, credit, advertising, installment buying and automobiles alongside barriers to prosperity, farmers' difficulties and declining heavy industry. Prohibition and bootlegging help explain organised crime and the federal response.
Compare modernity and tradition: the Scopes Trial, changing gender roles, flappers and opposition, the First Red Scare, the Second KKK, immigration restrictions, Red Summer and racial violence, Harlem Renaissance, New Negro movement and Native American citizenship under the Snyder Act.
Sources for this lesson
Pause and explain
What should a strong answer about american imperialism, the first world war and the 1920s do?
Worked example
Did the 1920s bring prosperity to all Americans?
Show the worked solution
- Compare national growth indicators with groups and sectors facing barriers.
- Connect policy and consumer change to the experiences of workers, farmers and minorities.
- Reach a judgement that distinguishes cultural change from economic security.
Answer Consumer goods and credit expanded for many, but farmers and heavy industry faced difficulties and prosperity was not evenly distributed. Nativism, racial violence and restrictions also shaped the decade. The 1920s changed consumption and culture while leaving significant economic and social divisions.
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Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Why did the US enter the First World War, and how did mobilisation affect Americans?
Give me a hint
Link the foreign-policy sequence to civil liberties and group experience.
Compare my reasoning
- Identify the issue and date range.
- Select named syllabus evidence.
- Explain what it shows and qualify the claim.
Wilson initially sought neutrality, but unrestricted submarine warfare, the Lusitania, anti-German feeling and the Zimmermann Telegram contributed to entry. Mobilisation brought propaganda, rationing and conscription, and restricted speech; it also changed women's roles, military service and migration while maintaining segregation.
Look for these in your work
- Uses specific evidence
- Explains the evidence's significance
- Keeps the conclusion within the period
How far did territorial expansion reflect economic motives?
Give me a hint
Compare markets and resources with strategy, national ideas and debates over citizenship.
Compare my reasoning
- Set a clear criterion for the question.
- Compare at least two pieces of evidence or perspectives.
- Make a balanced judgement and acknowledge a limit.
Economic motives such as markets and resources mattered, but so did nationalist ideas, military aims and the frontier narrative. The Spanish–American War, Roosevelt's policies and interventions show the interaction of these motives. Anti-imperialists challenged expansion, and territorial status raised questions about citizenship and rights.
Look for these in your work
- Compares relevant evidence
- Explains cause, change or consequence
- Reaches a reasoned judgement
Original practice claim (not a historical source): ‘The 1920s were modern, so traditional beliefs disappeared.’ Evaluate it.
Give me a hint
Use examples of innovation and resistance in parallel.
Compare my reasoning
- Identify the claim's assumption.
- Check it against named syllabus evidence and another perspective.
- Explain a balanced conclusion and any missing evidence.
Consumer culture, automobiles, flappers, the Harlem Renaissance and new media signalled change. Yet prohibition, the Scopes Trial, the Second KKK, immigration restrictions and opposition to women's new roles show that traditional beliefs and exclusion remained powerful. Modernity and tradition coexisted and conflicted.
Look for these in your work
- Identifies an assumption
- Checks more than one perspective
- States a supported, qualified conclusion
Common mistakes
- Calling US entry into war inevitable
- Treating imperial territories as empty strategic assets
- Equating consumer growth with equal prosperity or social acceptance
What can you explain now?
What were the causes and consequences of US territorial expansion in the late-nineteenth and early-twentieth centuries?
Compare with the explanation
Why did the US enter the First World War and how did the war impact Americans?
Trace US expansion and intervention, entry into the First World War and the uneven boom and cultural conflicts of the 1920s. Use foreign-policy decisions and varied American experiences to explain change without treating growth or wartime mobilisation as universal benefit.
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Make it stick
State the central issue in what were the causes and consequences of us territorial expansion in the late-nineteenth and early-twentieth centuries?, give one specific example from the syllabus and explain what would qualify your conclusion.
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