In December of 1965, Life magazine published a special issue titled “The U.S. City: Its Greatness Is at Stake.” The upshot was that America’s cities were on a “suicidal” course and bold new ideas would be needed to revive them. One such idea was the “linear city,” a structure that might be a mile wide and as much as 20 miles long containing every possible urban function. The version Life presented, illustrated with a cross section that made it look like a feverish ant farm, was cooked up by an uncredited team of Princeton professors that included the not-yet-famous Peter Eisenman and Michael Graves. Called the Jersey Corridor Project, it consisted of two parallel strips, one for industry and the other “a nearly endless ‘downtown’ of homes, shops, services” with highways in the basement, running like a ribbon through an otherwise pristine natural landscape.

The Jersey Corridor Project was not the first linear proposal. The earliest dates from 1882, when Spanish planner Arturo Soria y Mata envisioned a 30-mile-long city built along a Madrid tramline. Subsequent proposals inclu-ded Roadtown, Edgar Chambless’s dream of a skinny city following a railroad line, and Le Corbusier’s unbuilt 1930s scheme for Algiers that stacked highways atop housing leading to the suburbs. There’s actually a whiff of the linear city in New York, where four apartment blocks straddle the highway leading to the George Washington Bridge. In 1967, then-mayor John Lindsay was quite serious about building another one through Brooklyn:

A five-and-a-half-mile-long dense community was to be erected atop the under-construction Cross-Brooklyn Expressway. At the time, even the steadfastly sensible critic Ada Louise Huxtable supported the plan: “It almost seems to be in the cards, logically and inevitably…You can’t outlaw the 20th century.”

Predictably, Lindsay’s linear city was killed by the state legislature in Albany in 1969. It seems the concept more or less vanished with it. Except for one thing: Our Interstate Highway System, nearly 47,000 miles of it, is, by default, a linear city, longer than any wild-eyed visionary ever dreamed possible. In the development and population centers that have glommed on to the interstate over the years, you’ll see a messy, free-form version of what those 1960s planners were advocating. But what if we reexamined the interstate system and began to view it as a prospective place, one where people might want to live or work, or at least linger for longer than the ten minutes it takes to fill up the tank?

Lately, architects, planners, and inventors have taken notice of the highway system’s roughly two million acres of untapped capacity. The pioneers in this kind of thinking may have been the kids in San Diego who, in the 1990s,carved the Washington Street Skate-park from a no-man’s land beneath I-5. Now power companies are waking up to the highway’s possibility as a site for renewable energy, and designers have begun to see the potential of this vast reservoir of infrastructure and open space. After all, you can’t outlaw the 21st century.