Frederick Jackson Turner was perhaps the Midwest's most famous historian. In his time, as in ours, Americans were unsure of exactly what held their awkward federation together. At the close of the 19th century, Turner offered a beguiling answer — that the frontier environment of the Midwest and Far West had molded Americans into good republicans — a story that was incredibly popular, staggeringly influential and completely wrong.

It's a myth that's helped divert us into a dead end on the road to national unity and understanding — things desperately needed if we are to hold our divided federation together amid today's toxic politics and racist outrages.

During Turner's early childhood in Portage, Wis., the states were at war with one another over whether all humans were born equal with an unalienable right to liberty, as the Declaration of Independence had asserted, or if only those with certain bloodlines — white Anglo-Saxon Protestant, for instance — were meant to participate in the American experiment. While he was attending Portage High School, the former Confederate states won the peace when the Union gave up on "Reconstruction" — the effort to enforce the civil and political rights of African-Americans — in the face of the Ku Klux Klan's murderous terrorism campaign.

Half the country embraced a legally sanctioned apartheid regime, which the other half accepted as being consistent with American ideals.

In graduate school at Johns Hopkins University in 1888, Turner befriended his instructor and fellow boardinghouse resident, a Southerner named Woodrow Wilson, who would go on to segregate the federal government and champion a 1915 blockbuster film, "The Birth of a Nation," that glorified the KKK's reign of terror and the reinstitution of formal white supremacy in the South.

The protests over the screening of this film — based on a book by another of Wilson's graduate school friends, Thomas Dixon Jr. — prompted violent police responses and the explosive growth of both the National Association for the Advancement of Colored People and the second KKK.

In this convulsive national environment, Turner's most famous work was greeted with bipartisan, pan-regional rapture.

Turner was the first chronicler of U.S. nationhood to shift the center stage of the story from the tensions between the Northeast and Southeast to what he first believed was the unifying environment of the Midwest and Far West.

His seminal essay, which Turner first presented at the 1893 Chicago World's Fair, argued this region — not New England or the Chesapeake country — was the real place of America's birth. Even the slavery question itself, when "right viewed," became but "an incident" in the United States' story. For when westward-bound settlers poured over the Appalachian Mountains and into the "frontier" of the vast Mississippi River watershed, the environment they encountered forced them to finally leave the fingerprints of the Old World behind, to embrace self-reliance and independence, qualities Turner argued fostered democracy, democratic constitutional arrangements and the vigorous local civics he had grown up with in Portage.

His thesis statement, which would be quoted in a thousand future textbooks and academic papers: "The existence of an area of free land, its continuous recession, and the advance of American settlement westward explain American development."

The West, Turner thought, was an Eden that had forced Americans to adapt to primitive conditions, a return to innocence and virtue that shaped the U.S. character. Settlers were taken "from the railroad car," stripped of "the garments of civilization" and placed in "the birch bark canoe" and "the hunting shirt and the moccasin." Soon, they were "planting Indian corn and plowing with a sharp stick" and shouting war cries.

Faced with Native American resistance — Turner never much considered their part in the story or what their extirpation might say about the American character — the settlers looked to the U.S. government for protection, fostering loyalty to the nation, and not to their half-forgotten state of origin.

Turner's idea spread like wildfire, especially after he used it to explain the rise of Midwestern populism ahead of the 1896 presidential election in an article for the Atlantic. He had formulated his theory at exactly the time that the U.S. — an industrializing, urbanizing, continent-spanning, immigrant-attracting Goliath — needed a new origin story that could explain how it had gotten to where it was and where it might be going.

Americans, having weathered the Civil War and its untidy aftermath, were reassured that their nation's destiny was to be the torch bearer of freedom in the world, and Turner had provided a rationale that didn't rely on the fuzzy metaphysics of Protestant theology or Divine Will — as early 19th century intellectuals had — but rather the latest scientific doctrines: environmental adaptation and evolution. Academics, journalists, teachers and textbook writers embraced and propelled it into the popular psyche, where it remains.

As a researcher, however, Turner had lost interest in the frontier almost as soon as he had returned from the World's Fair. He was focused on what he was beginning to realize was an even more consequential aspect of America's Westward colonization experience: sectional differences.

Turner by now had come to realize that when he had developed his frontier thesis, he had been relying on the experiences of his own tier of "the West," a swath of territory that included Wisconsin, Michigan, Minnesota and parts of Ohio and Illinois and had been colonized by a settlement stream originating in New England, one that included all of his own English Puritan ancestors.

As he poured over new maps of soil geography compiled by the Department of Agriculture, and the color county-level maps of voting patterns, economic characteristics and social behavior in new editions of Scribner's Statistical Atlas of the United States or Appleton's' Annual Cyclopedia, Turner saw that other parts of "the frontier" had been settled by entirely different peoples.

Parts of the frontier that had been settled by the settlement stream anchored in the Quaker-founded mid-Atlantic (Iowa, the middle parts of the Lower Great Lakes States and parts of the Plains) or from Scots-Irish settled Appalachia (the lower tiers of Ohio, Indiana, Illinois and Missouri) behaved completely differently, be it in political choices, cultural attitudes, or interest in local civics.

Turner spent the last decades of his life working on what he intended to be his magnum opus, a book on the abiding differences between these regional cultures. "The whole history of American politics needs to be interpreted in the terms of a contest between these rival economic and social sections," some of which were comparable to "the greater nations of Europe," he advised his fellow scholars. "Congressional legislation will be shaped by the compromises and combinations, which will in effect be treaties between rival sections, and the real federal aspect of our government will lie not in the relation of state and nation, but in the relation of section and nation."

But like a band that can't escape the shadow of its early No. 1 hit, Turner couldn't get Americans interested in his new argument. The Frontier Thesis was all the rage and the differences between the regions were, he was told more than once, withering away in the face of the unifying power of the telegraph, railroads, radio, universal education, rural mail delivery and motion pictures. When he died in March 1932, his book was still unfinished.

America carried on, many of its people having convinced themselves in midcentury that they belonged to an increasingly unified nation, that the differences between the Deep South and New England, the Appalachian-settled Ozarks and the Yankee-settled Upper Great Lakes states were vanishing.

But the separate settlement legacies remained, festering below the surface, and soon to express themselves in county-level maps of red and blue, in prevailing attitudes toward mask-wearing, and in divergent levels of enthusiasm for a demagogic presidency.

Colin Woodard is the author of six books, including "American Nations: A History of the Eleven Rival Regional Cultures of North America," and the newly released "Union: The Struggle to Forge the Story of United States Nationhood," upon which this essay is adapted.