We humans are tribal people, organizing ourselves into bands and clans that divide the world into us and them, self and other: Goths. Bloods. Rotarians. Where blood is not the basis, something else becomes the point of division: a haircut or tattoo, a band or political issue. And for all our talk of the oneness of humankind, we seem to thrive on making such distinctions.

Theodore Geisel, Dr. Seuss, got it right in his prescient story from 1953, The Sneetches, in which curious yellow creatures follow an apartheid based on whether they sport green stars in their navels. A dozen years later, about the time Seuss’ first readers were approaching young adulthood, Susan Eloise Hinton, herself a teenager, began writing a story with echoes of Romeo and Juliet by way of West Side Story and of Lord of the Flies alike, recounting the clash between tribes in the rough and tumble of Oklahoma.

“I am a greaser,” says Sodapop, one hero of S.E. Hinton’s The Outsiders. “I am a JD and a hood. I blacken the name of our fair city. I beat up people. I rob gas stations. I am a menace to society. Man, do I have fun!” There’s no Officer Krupke as a foil, but Sodapop’s self-mockery speaks to the way straight-and-narrow Tulsans view his kind, kids who hang out in machine shops and garages with cigarettes rolled up in their sleeves, kids whose only path out of the grittier part of town is the Army or prison.

The Greasers face off whenever they can against the Socs, the upper-society kids who drive Mustangs and wear Madras shirts. Fittingly for the time, they fight a war that is not about winning hearts and minds but instead about attrition. Ponyboy Curtis, the youngest of three brothers left orphaned by a car crash—and while juvenile literature very often presumes the death of one parent, it rarely kills off both—likes to go to the movies. So do the Socs, and when a bunch of them beat Ponyboy up after a show, it’s time to escalate from fists to knives and guns. The conflict swirls while Ponyboy wrestles not just with the problem of staying healthy and alive and out of jail, but also the usual teenage stuff: pining for a Soc girl his age who’s not like the others, doing his part in the parentless but not leaderless household the Curtis brothers have made for themselves, scraping out overdue English compositions.

Published on April 24, 1967, The Outsiders was an immediate hit. I read it when it first came out in paperback, about the time I began to sort out what my own tribe might be. (Its members smoked pot, drank good coffee, opposed the war, and read poetry.) The book has since come under regular assault from censorious civilians who wish to see it banned from schools and libraries for its language, its forbidden substances, its uncompromising look at the violence disaffected young people can and do commit. But it remains in print 50 years on, changing the lives of its readers, truly a modern classic and well-deserving of that name.

Gregory McNamee is a contributing editor.