20th-Century U.S. History for the Civics Test - World Wars to 9/11

Updated: October 30, 2026

The 2025 civics test has a full section called "Recent American History," covering the 1900s and early 2000s: World War I, the Great Depression, World War II, the Cold War, the Korean and Vietnam Wars, the Persian Gulf War, and September 11, 2001. Most questions ask why the U.S. entered a war, so learn the reason, not just the dates.

Wars of the 1900s

For "Name one war fought by the United States in the 1900s," USCIS accepts World War I, World War II, Korean War, Vietnam War, or (Persian) Gulf War. Here is each one in brief.

World War I (U.S. involvement 1917 to 1918)

War broke out in Europe in 1914. The U.S. stayed neutral at first but entered in 1917.

Why did the United States enter World War I? Accepted answers:

Because Germany attacked U.S. (civilian) ships
To support the Allied Powers (England, France, Italy, and Russia)
To oppose the Central Powers (Germany, Austria-Hungary, the Ottoman Empire, and Bulgaria)

Women win the vote (1920)

Shortly after the war, the 19th Amendment (1920) gave women the right to vote nationwide. For "When did all women get the right to vote?" USCIS accepts 1920, after World War I, or (with the) 19th Amendment. The movement's roots go back to the 1800s leaders covered in the Civil War and the 1800s.

The Great Depression (1929 to the late 1930s)

What was it? The longest economic recession in modern history.
When did it start? With the Great Crash (1929) or the stock market crash of 1929.

Millions lost jobs, savings, and homes. President Franklin D. Roosevelt, elected in 1932, responded with the New Deal, a series of federal programs and reforms, including Social Security.

World War II (U.S. involvement 1941 to 1945)

On December 7, 1941, Japan attacked the U.S. naval base at Pearl Harbor, Hawaii, and the United States entered the war.

Why did the United States enter World War II? Accepted answers:

(Bombing of) Pearl Harbor
Japanese attacked Pearl Harbor
To support the Allied Powers (England, France, and Russia)
To oppose the Axis Powers (Germany, Italy, and Japan)

Who was president during the Great Depression and World War II? (Franklin) Roosevelt. He was elected four times, the only president to serve more than two terms. That led to the 22nd Amendment, which now limits presidents to two terms (see the three branches of government).

Dwight Eisenhower

Eisenhower was the Supreme Allied Commander in Europe during World War II, leading the D-Day invasion in 1944, and later the 34th president (1953 to 1961). Accepted answers:

General during World War II
President at the end of (during) the Korean War
34th president of the United States
Signed the Federal-Aid Highway Act of 1956 (created the Interstate System)

The Cold War (about 1947 to 1991)

After World War II, the United States and the Soviet Union became rivals, competing for global influence without fighting each other directly.

Main rival during the Cold War? Soviet Union, USSR, or Russia
One main concern of the United States? Communism or nuclear war

Two "hot" wars came out of this rivalry, and both have the same answer:

Korean War (1950 to 1953): Why did the U.S. enter? To stop the spread of communism.
Vietnam War (U.S. combat role mainly 1960s to 1973): Why did the U.S. enter? To stop the spread of communism.

The Cold War ended with the collapse of the Soviet Union in 1991.

The civil rights era

The 1950s and 1960s were also the era of the civil rights movement and Martin Luther King, Jr. This has its own guide: the civil rights movement on the civics test.

The Persian Gulf War (1990 to 1991)

In 1990, Iraq invaded its neighbor Kuwait. A U.S.-led coalition responded in early 1991.

Why did the United States enter the Persian Gulf War? To force the Iraqi military from Kuwait.

September 11, 2001

This is an asterisk question, so it is also on the 65/20 list. What major event happened on September 11, 2001, in the United States? Accepted answers:

Terrorists attacked the United States
Terrorists took over two planes and crashed them into the World Trade Center in New York City
Terrorists took over a plane and crashed into the Pentagon in Arlington, Virginia
Terrorists took over a plane originally aimed at Washington, D.C., and crashed in a field in Pennsylvania

The shortest answer, "Terrorists attacked the United States," is all you need.

Name one U.S. military conflict after the September 11, 2001 attacks. (Global) War on Terror, War in Afghanistan, or War in Iraq.

American innovations

The section also includes "Name one example of an American innovation." Accepted answers: light bulb, automobile (cars, internal combustion engine), skyscrapers, airplane, assembly line, landing on the moon, or integrated circuit (IC). "Airplane" (the Wright brothers, 1903) and "landing on the moon" (Apollo 11, 1969) are easy to remember.

A timeline to memorize

1917: U.S. enters World War I
1920: 19th Amendment, women vote
1929: stock market crash, Great Depression begins
1941: Pearl Harbor, U.S. enters World War II
1950: Korean War begins
1960s: Vietnam War, civil rights movement
1969: moon landing
1991: Gulf War, end of the Soviet Union
2001: September 11 attacks

How to study this section

Group the "why did the U.S. enter" questions together: WWI (German attacks on ships), WWII (Pearl Harbor), Korea and Vietnam (stop communism), Gulf War (force Iraq out of Kuwait). Five wars, four reasons. Then mix them back into the full civics questions list so you can recognize them in any order, which is what a randomized Exam Mode in an app like Civio is for. For a full schedule, see the 30-day study plan.

Frequently asked questions

Why did the U.S. enter World War II?

The main answer is that Japan attacked Pearl Harbor. USCIS also accepts "to support the Allied Powers" and "to oppose the Axis Powers (Germany, Italy, and Japan)."

Who was the main rival of the U.S. during the Cold War?

The Soviet Union. USCIS also accepts USSR or Russia.

Why did the U.S. enter the Korean and Vietnam Wars?

For both wars, the accepted answer is to stop the spread of communism.

What happened on September 11, 2001?

Terrorists attacked the United States. They hijacked planes and crashed them into the World Trade Center, the Pentagon, and a field in Pennsylvania.

When did the Great Depression start?

With the stock market crash of 1929, also called the Great Crash.

Prepare for the civics test with Civio: every official question from the 2025 USCIS civics test, Exam Mode with your state's questions, and spaced repetition.

Informational article, not legal advice. Civio is not affiliated with USCIS or any government agency; always check current requirements at uscis.gov.