The United States is known as a nation of immigrants, but as Erika Lee shows, an irrational fear and hostility toward immigrants has been a defining feature of our nation from colonial times to the Trump era. Widespread anxiety over Irish Catholics turned xenophobia into a national political movement, while Chinese immigrants were excluded, Japanese incarcerated, and Mexicans deported. Today, some Americans fear Muslims, Latinos, and the so-called browning of America. Forcing us to confront this history, Lee explains how xenophobia works, why it has endured, and how it threatens the nation's founding principles.