Some objects are so familiar and so ordinary that it seems impossible to imagine that they did not always exist. Take the school backpack, for example. Its invention can be traced to one man, Murray McCory, who died last month. McCory founded JanSport in 1967 with his future wife (Jan, the company’s namesake). Until JanSport evolved the design, a backpack was a bulky, specialized thing for hiking, used only by smelly people on mountain trailheads or European gap years. By the time I entered school, the backpack was lightweight and universal. What did anyone ever do previously?

They carried their books. Let me repeat that they carried their books. In their arms, or under them. I still cannot fully process that this was the case, even though I have seen countless depictions of it in film and on television. A boy carries textbooks at his side, as one would a skateboard. A girl clutches hers to her chest. The boy offers, as an ancient courtship ritual, to carry the girl’s for her. Multiple books might have been lashed together with a belt. These are not retrofuturist myths but acts that children really did.

Some used bags, sure. They probably called them satchels—a word my dad would say. But many still wandered the halls and the quads in ignorance. Like fish in water, they probably thought nothing of it, just as their forebears thought nothing of life without electricity.

The 20th century was an incredible time to live in, because so much was possible yet undone. Automobiles and airplanes, sure, but also every electrical appliance and the lifestyles they made possible. Once you have airplanes and airports, for example, the opportunity arises to put wheels on the bottom of suitcases. It’s obvious. And yet, it once wasn’t. The rolling carry-on made sense only after air travel became common, causing airline terminals to become more extensive and luggage handling to get insourced to passengers. But once it did (1987, it turns out), the Rollaboard changed the nature of travel. Your belongings, an extension of yourself, got to take a trip of their own, and you gained some control of a voyage otherwise out of your hands.

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Such a circumstance made the school backpack possible too. McCory was a Seattle-area native and attended the University of Washington. Pacific Northwesterners have a reputation for outdoorsmanship, and the classic hiking backpacks—with their large, rigid frames—were familiar to McCory (who also invented the dome-shaped tent). Once JanSport figured out how to make a lightweight backpack suitable for carrying books and supplies, it sold the product at the University of Washington bookstore. There, more stereotypically outdoorsy youths surely understood the pitch intuitively.

JanSport’s rucksack spread nationwide from there. Its debut coincided with a historic boom in higher-education enrollment: Once limited to the aristocracy, by the 1960s, college had become affordable and viable for the millions of Baby Boomers who enrolled in large numbers. The backpack was the perfect accessory for expressing this newfound casualness of college life, and it also aligned with the thriving hippie counterculture; these students, who were now buying backpacks, were also more oriented to the outdoors (or at least to dirt). With a backpack on one’s shoulders, the campground colonized campus, bringing it down to earth in a literal and symbolic sense. Now only the Man would use a satchel.

In the ’80s, the backpack-toting campus hippies became yuppies with suburban homes and kids of their own. They passed on the school backpack to their offspring, making it universal in primary and secondary schools. The new circumstances changed the backpack; it evinced aspiration more than sincerity. School was serious business, undertaken to climb the next rung on the ladder. Accordingly, school backpacks offered a literal and symbolic representation of burden, young lads and lasses hauling their books on sore, ambitious shoulders. The unsavory listlessness of the overstuffed frame backpack had, in half a generation, given way to the limitless aspiration of the grade-school rucksack.

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Sometimes I feel like everything worth inventing has already been invented, and mostly in the prior century. But that intuition is wrong. Ordinary things evolve constantly, and their meanings chameleon accordingly. Against all odds, backpacks also became fashion, worthy of Prada emblems. Loungefly turned them into expensive souvenirs, bought at Disneyland but never used again thereafter. The would-be tech titan Millennials (who are the children of the yuppies who first bore books on their backs) sometimes cart lanky, hypermodern ones containing not notebooks but notebook computers. On their bodies, backpacks now symbolize the ease with which those machines can be made to do anything.

Even I have been surprised at the depths of the backpack’s limitless potential. After writing about the carry-on bubble earlier this year for The Atlantic, I gave up my rolling luggage for a new kind of hybrid backpack-suitcase that can carry my computer, toiletries, and a few days’ clothes without wrinkling them. I smirk at the foolish rabble, still giving their garments a ride while lugging Murray McCory’s invention as well, as I stow my whole trip underseat. Glory to the backpack, which JanSport once made surprising, and which still carries secrets.