World History · Era— 1900 — present —

The century that remade everything.

Two world wars, the Holocaust, the Cold War, decolonization, civil rights, the rise of Asia, climate, technology, globalization. The era we are still living in — and still trying to make sense of.

What you need to know

The twentieth century broke the long 19th. World War I ended European hegemony; the Great Depression broke the gold-standard global economy; World War II and the Holocaust forced a moral reckoning that produced the United Nations and the postwar human-rights regime. Decolonization (1947–1975) replaced empires with nation-states. The Cold War (1947–1991) divided the world into superpower blocs and proxy wars. China rose. The Soviet Union fell. Globalization, climate change, the internet, and the resurgence of authoritarianism define the era we are still inside of.

Key developments (7)

The era, topic by topic.

  • 1.

    World War I

    The end of the long 19th century. Empires fall; the U.S. emerges; Versailles fails.
  • 2.

    The interwar crisis

    Depression, fascism, Stalinism — democracy on the back foot in most of the world.
  • 3.

    World War II and the Holocaust

    60 million dead. A new moral framework. New superpowers.
  • 4.

    Decolonization

    1947–1975. India, Pakistan, Ghana, Algeria, Vietnam — empires unwind.
  • 5.

    The Cold War

    Two superpowers, ideological blocs, proxy wars from Korea to Angola.
  • 6.

    Globalization and China’s rise

    1980s onward. Manufacturing shifts east; the U.S. and China entangle.
  • 7.

    The era we’re in

    Climate, authoritarianism, the internet, AI — the 21st century’s open questions.
Every history class is also a history of the present. Right now, that present is a hundred-year-old story still being written.

Where this era shows up in your courses

APWH:Units 7–9 cover this entire era.

APUSH:Periods 7–9.