It’s a commonplace of anthropology that it often takes an outsider to show a group of insiders what it’s up to. One of the best books I know concerning Catholic pilgrimage in Europe, for instance, was written by a Jewish scholar from Brooklyn. One of the most compelling books ever written about the Arab world was written by a shy young man from the minor Irish nobility. An Italian Jesuit penetrated the mysteries of early modern China. And so on, all pointing to the fact that sometimes we need the Other to show us just how otherly we are.

So it was when the photographer Robert Frank arrived in the United States in 1947. Born in Zurich to a German Jewish father and Swiss mother, Frank moved to New York, then, as now, the true capital of the world, in his early 20s. He found work as a fashion photographer, but that wasn’t quite his calling, and he soon took to the road, traveling around the world and then returning to his adopted country and securing a Guggenheim Foundation grant to document its highways and byways. In 1955 and 1956, he undertook a Kerouac-ean journey across a wide swath of the heartland, culminating when, on his return to New York with a portfolio in hand, he ran into Jack Kerouac himself, who took a look and offered to write an accompanying text.

The result was the book The Americans (Steidl, $35), first published in France in 1958 and in this country in 1959, and reprinted many times since. It was not the image many Americans wanted to see of their country, far from triumphalist, far from proclaiming the superiority of the American way of life in those Cold War years. The heavily accented Frank had had unhappy encounters on his journey. In Arkansas, he had been jailed for no reason other than that he looked like a threat to homeland security; in Mississippi, he was waylaid by white teenagers who accused him of looking like a Communist and told him, “Why don’t you go to the other side of town and watch the n—s play?”

And so Frank did, returning with black and white photographs of black and white Americans who looked suspiciously, and often angrily, across the color line at one another. Indeed, about the only subject in his portfolio who does not look vexed is lying dead. Using a 35 millimeter camera and high-grain film, often shooting in dim light and surreptitiously, Frank recorded a nation very nearly at war with itself, worried sick and spoiling for a fight, a place where hardly anyone smiled—producing, in the end, what Kerouac called “a sad poem right out of America onto film, taking rank among the tragic poets of the world.”

The 55 years that have followed Frank’s poem—and so it is—would seem to have brought no more cheer to this corner of the world. An enterprising shooter could do worse than undertake a re-photographic project in Frank’s footsteps, recording a nation that seems poised to tip into civil war, still suspicious, still angry. The Americans remains an essential portrait from the outside in.