The Civil War proved a turning point. "Before the war, it was said 'the United States are,'" the late historian Shelby Foote said. "After the war, it was always 'the United States is,' as we say today without being self-conscious at all. And that sums up what the war accomplished. It made us an 'is.'"

The truth is not quite so black and white, but the overall trend is clear. As the country moved through Reconstruction and the Progressive Era, the use of the singular became more and more common. By World War II, the use of the plural practically fell out of use altogether. The creation of a strong, unified national identity, hundreds of years in the making, parallels the move from the plural to the singular.

That is, up until the modern age. Beginning in the 1980s, the trend away from local identities and toward a strong national one began to decline -- a shift apparent in the increasing polarization of American politics. With less and less uniting them, a significant portion of the populace began to grow apart. With this divide, the plural form reemerged.

Definitive data on such trends is, of course, hard to find. But a cursory search through the University of California's The American Presidency Projectarchives reveals that, of all the presidents, Ronald Reagan used the plural form most. Given that Reagan presided over the beginnings of the modern era of polarization, this is not a big surprise. And coming in second place? Barack Obama.

Indeed, it turns out that Obama's first use of the phrase was in April 2010, with a rather mundane Loyalty Day Proclamation -- which, oddly enough, focused on defining what it was Americans had in common. Since then, he's used the phrase a handful of times.

On the one hand, this in itself should not be all that surprising. With Americans divided over everything but our shared disdain for Congress, it makes sense that we might be drawn back into a federalist model of national identity, into thinking of the nation in the plural.

But it is surprising to see Obama reflect the shift. After all, he has long tied his identity to the unity of the nation. Obama's own story, he said in 2008, "has seared into my genetic makeup the idea that this nation is more than the sum of its parts -- that out of many, we are truly one." In voting for Obama, Americans were voting for unity, for a president who could begin to heal our divisive wounds.

That was the hope. But it has not come true.

Obama would surely resist the characterization that our national identity is in danger of splintering, as he has publicly done again and again. But his language takes us back to the days before the Civil War, to a time when Americans' identities were marked more by their differences than their commonalities. And perhaps, despite our hopes, that's the actual direction we're heading.

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