For much of America’s history, the country was literally expanding. There was always a frontier to conquer, always new land to claim (at least for white people), and the promise of America was in its never-ending growth. But now, that optimism has been replaced by the politics of scarcity and Donald Trump’s border wall. What has changed?

That’s the question at the center of a new book, The End of the Myth: From the Frontier to the Border Wall in the Mind of America, out March 5 from historian Greg Grandin. He conceived of the book during the campaign, when Trump turned the wall into the preeminent symbol of his candidacy. To Grandin, the dichotomy between that wall and the mythical frontier—which represented the politics of expansion—explained a lot about Trump’s appeal and the new direction of the country. VICE recently talked to Grandin about the book and how to understand Trumpism as a break from the past.

VICE: How has the frontier functioned in American history?

Greg Grandin: If you just go back to Andrew Jackson in the 1820s and the 1830s, they were able to give white, property-less men the vote and expand political democracy without having to worry about them voting into power a labor party. There was all that worry that if you expanded the democracy to the unpropertied they'd vote for socialists. Access to the frontier was a way of avoiding that problem. If you gave them the vote, but also gave them land, then the land would act as a safety valve.

In some ways, this is the roots of the deep association between individual rights and violence against people of color, because it was founded in the country's removal policy. The displacement and ethnic cleansing of Native Americans by white settlers becomes the foundation of Jacksonian democracy. Wars on the frontier create quite a bit of extremism and racism. But that can always be rolled over into the next war. As long as there was another war in the future, that extremism could be kind of vented outward.

How has that dynamic changed?

Even though the US is still at war, war no longer serves as the kind of ideological crusade to vent extremism outward. Trumpism is what happens when the extremism generated by war gets turned inward with no vent possible. It predates Trump, but this goes back to the Obama administration, with Trump's origins, and all the racist hysteria that was directed at Obama.

How engrained in our culture is the frontier myth, and how have we used it to avoid issues that are now so relevant?

Expansion allows for an avoidance, a great evasion, from having to deal with social questions. You can always promise a policy of endless growth and expansion. This is the height of Clintonism in 1990s: The idea that inner-city problems are going to be solved not through attacking the structural foundations of racism and exploitation at home, but through economic globalization. We can talk about race, but nobody talks about expansion, nobody talks about militarism, nobody talks about what it means that the promise of endless economic growth is no longer the way that one can respond to social demands. Looming over all of this is the reality of climate crisis. That's the real end of the road.

What do you think Trump's wall means to the American dream? Does it effectively kill it, and the endless promise our country has thrived on?

I think it’s a symbol of a certain kind of disenchantment, a disillusionment, an end to the idea of limitlessness, and end to the kind of politics that can be organized around the promise of limitlessness. The frontier stood for that promise of limitlessness, of moving forward in the world. I think the wall is in some ways an acknowledgement that it was an illusion, that there are limits. But on the other hand, it's also its own form of illusion. It promises its own kind of freedom, at least the guise of universalism, like the old multilateral order did, but a very nativist notion of freedom.

I think Trump is good at playing to the fears of his base. In the world of limits we have to hunker down and take care of our own. We can no longer have a politics or a policy that is so generous—that's the way it's presented. He's good at playing to those fears and that kind of subconscious understanding that there are limits. But on the other hand, Trump himself is kind of a symbol of impunity, that he can get away with everything, that there are no limits, right? As he said, I could walk down Fifth Avenue and shoot somebody in the face, and I wouldn't lose political support.

After somebody reads your book, what do you want them to come away with?

I hope that the book helps them move beyond those kind of binary debates between race and class, or debates that either say Trump is wholly exceptional and a break with the traditions of the United States or that he’s a fulfillment of its darkest history. The way that I’d hope they would move beyond those debates is by realizing the centrality of expansion in US history, and the possibility of expansion. One of the things that makes the United States unique is that it had access to the world, and to the promise of moving out into the world, that no other nation in the 20th century had. It's a different way of thinking about US history and the current moment, this choice that a new generation is facing, between social democracy on the one hand, represented by [Bernie] Sanders and [Alexandria] Ocasio-Cortez, and barbarism, on the other hand, with Donald Trump.

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