The 20th century refers to the hundred-year period from January 1, 1901 to December 31, 2000. This might seem confusing at first: why isn't the 1900s called the 19th century? The reason is that we count centuries starting from year 1, not year 0. So the first century covered years 1 through 100, the second century covered 101 through 200, and so on. By this counting, the 1900s became the 20th century.

The 20th century was one of the most transformative periods in human history. It began with people traveling by horse and carriage and ended with the internet connecting homes around the world. During these hundred years, humans invented airplanes, computers, antibiotics, television, spacecraft, and countless other technologies that changed daily life.

The century also witnessed tremendous hardship and conflict, including two world wars that affected nearly every nation on Earth. But it also saw remarkable achievements: humans landed on the moon, diseases like polio were nearly eliminated, and billions of people gained access to education and opportunities their ancestors never had.

When someone mentions “20th-century music” or “20th-century literature,” they're talking about creative works from this era. When historians discuss “20th-century America,” they mean the United States during the 1900s, a period that included everything from the Great Depression to the Civil Rights Movement to the rise of Silicon Valley.