In the 19th century, especially, school textbooks emphasized America's innate superiority. "What is the national character of the United States?" asked an 1825 geography text. In the next sentence, it gave the book's only correct answer: "More elevated and refined than that of any nation on earth."
After the Civil War, to be sure, Northern and Southern textbooks taught divergent stories about America's great sectional conflict. Within each region, students received a single perspective rather than a variety. Below the Mason-Dixon Line, the term "Civil War" itself became taboo; texts called it the "War Between the States" or the "War of Yankee Invasion." Northern books were friendlier to the Union cause, but they ignored or denigrated African-Americans' efforts on behalf of the war as well as their tribulations after it.
In the early 20th century, a new generation of self-described "Progressive" historians began to question the sunny national narrative. During the American Revolution, they pointed out, one-third of Americans fought on the English side. After the war, the Progressives argued, rich Americans drafted a Constitution that protected their wealth from a rabble they reviled.
Some of this critique made its way into textbooks. But it disappeared in the 1920s, when a wide range of ethnic groups - including Poles, Germans, and blacks - joined hands against the new interpretation of the American Revolution. Poles rallied around Thaddeus Kosciusko; Germans celebrated Friedrich von Steuben; African-Americans venerated Crispus Attucks. All of these heroes had fought for the Revolution, and in the minds of ethnic minorities, any diminution of the larger cause would also diminish these figures' special contribution to it.