The political history of the US from the late 1830s through the 1850s is one long tragedy. President after president struggled to hold together an increasingly polarized nation. None served more than one term, two died in office -- and by 1860 the country was falling apart.

We hear a lot these days that we’re in a new age of polarization, with measures of partisanship showing a divide greater than at any time since the Civil War. But there’s a striking difference: It’s pretty clear what the polarization of the 1830s through 1850s was about. Nowadays that’s much harder to figure out.

All this is on my mind because I’ve just spent several days driving up and down Interstate 95 listening to Lillian Cunningham’s “Presidential” podcast. Cunningham is a reporter and editor at the Washington Post, and since the beginning of the year she has been offering up weekly 30- to 45-minute examinations of the presidents, in chronological order (she’s currently on Harry Truman). I highly recommend them.

For reasons not worth going into here, I decided to start with Martin Van Buren, who was elected in 1836. Van Buren had just finished serving a term as Andrew Jackson’s vice president; before that he had built the political machine that got Jackson elected. He’s considered the inventor of modern party politics. But his presidency started with the worst economic downturn the young nation had yet experienced and never really got much better -- with a standoff over whether to admit Texas to the Union as a slave-holding state one of the signature issues.

After that I really had to hear what came next. I skipped Van Buren’s successor, William Henry Harrison, because he died just 32 days after taking office, and went straight to John Tyler. Then it was James Polk, Zachary Taylor, Millard Fillmore, Franklin Pierce and James Buchanan. Failure after failure after failure.

Well, not Polk. During his one term, from 1845 to 1849, the US annexed Texas, wrested the territories of Nuevo Mexico and Alta California from Mexico, and cut a deal with Britain for the parts of the Oregon Territory below the 49th parallel. Polk created the modern, continent-spanning US -- and probably would have been re-elected in 1848 if he hadn’t held to his pledge to serve just one term. But even he didn’t do anything to resolve the great conflict tearing the country apart. In fact, his acquisitions provided lots of new territory to fight over.

The conflict was over slavery, and whether it would be allowed to spread. Since the Missouri Compromise of 1820 the basic idea had been to balance political power between the North and South by keeping the number of free and slave states equal. By the late 1830s, westward expansion was testing this balancing act, and by the mid-1850s it had completely broken down -- with Harriet Beecher Stowe’s “Uncle Tom’s Cabin,” published in 1852, sharply reducing the Northern appetite for compromise and the Kansas-Nebraska Act of 1854 turning the slave-versus-free-state deliberations into a bloody free-for-all.

Or something like that. I make no claim to expertise on this period. Apart from a couple of books read years ago and a bunch of Googling over the past few hours, my knowledge really is based entirely on “Presidential” podcasts. In those podcasts, one of Cunningham’s interviewees (a mix of historians and Post colleagues) will occasionally remark that some long-ago conflict or sign of political dysfunction is reminiscent of today. I kept being struck, though, by the differences.

Back then it really was all about slavery. And because of slavery, the South became utterly different from the North, with the differences only growing as the North industrialized and urbanized while the South stayed agricultural and rural. They were two countries, quite foreign to each other.

Now, by contrast, I’m hard-pressed to describe the single great ideological divide across which Americans have become so polarized. Sometimes it’s religious versus secular. Sometimes it’s educated versus less-educated. Sometimes it’s pro-immigration versus anti. Sometimes it’s big government versus small government. Sometimes it’s gun-toters versus gun-controllers. Sometimes it’s fossil-fuel fans versus windmill-lovers. Sometimes it’s old versus young. Sometimes (not much, actually) it’s rich versus poor. I’m sure you can come up with lots more.

As for geographic differences, too, coasts versus center and North versus South come up a lot, but it’s easy to find exceptions. Urban versus rural -- or, more accurately, cities and inner suburbs versus outer suburbs and exurbs, because rural areas now account for a small and shrinking share of the population -- may be the most consistent divide. It’s an economic divide, too, with growth increasingly concentrated in a few big metropolitan areas, and cities gaining (by some metrics, at least) on suburbs.

It’s really hard to envision the nation’s exurbs going to war with its cities. That seems reassuring -- we’re probably not on the verge of another civil war! But it’s also puzzling. What exactly is it that we’re all so angry at each other about then?

By Justin Fox

Justin Fox is a Bloomberg View columnist. He was the editorial director of Harvard Business Review and wrote for Time, Fortune and American Banker. He is the author of “The Myth of the Rational Market.” -- Ed.

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