There it sat on a library cart with 50 other elementary, grammar, and high-school history textbooks, its bright red spine reaching out through time and space. As I opened the book’s crisp white pages, it all came back. My loud gasp startled those near me at the special collections department of Harvard University’s Monroe C. Gutman Library. Exploring the New World — published repeatedly between 1953 and 1965 — had been assigned in my fifth-grade social-studies class in Saratoga, Calif.

As part of a broader study of the legacy of the antislavery movement and the rise of the modern civil-rights era, I wanted to assess how abolitionism had been presented in textbooks. I imagined a quick look. Instead, I found myself immersed in Harvard’s collection of nearly 3,000 U.S. history textbooks, dating from about 1800 to the 1980s. Without intending, I had become engaged in a study of how abolitionism, race, slavery, and the Civil War and Reconstruction have been taught for generations.

After reviewing my first 50 or so textbooks, one morning I realized precisely what I was seeing, what instruction, and what priorities were leaping from the pages into the brains of the students compelled to read them: white supremacy. One text even began with the capitalized title: "The White Man’s History." Across time and with precious few exceptions, African-Americans appeared only as "ignorant negroes," as slaves, and as anonymous abstractions that only posed "problems" for the supposed real subjects of history: white people of European descent.

The assumptions of white priority, white domination, and white importance underlie every chapter and every theme of the thousands of textbooks that blanketed the country. This is the vast tectonic plate that underlies American culture. And while the worst features of our textbook legacy may have ended, the themes, facts, and attitudes of supremacist ideologies are deeply embedded in what we teach and how we teach it.

Scholars often bemoan their lack of influence: embarrassing book sales figures and the like. Yet my review of American textbooks revealed that historians of the 20th century exerted an enormous impact on the way Americans have come to understand their history. The results are painfully evident. Their work either filtered down into schools, as interpreted by educators, administrators, and popular authors, or appeared directly: Ph.D.-trained scholars wrote many of the textbooks I read. To appreciate why white supremacy remains such an integral part of American society, we need to appreciate how much it suffused our teaching from the outset. ...