THE INTELLECTUALS DISCOVER THE LOOP.

Ferroequinologists generally know this story.  It is useful, none-the-less, for people whose interests run off the rails to know it as well.

The best transit systems don’t just haul passengers — they become symbols of their cities. In San Francisco, it’s the cable cars gliding gracefully over the steep hills. In London, it’s the bright red double-decker buses rolling past such landmarks as Big Ben. In Chicago, it’s the CTA cars rumbling and screeching over the Loop elevated tracks.

In the Loop, the French artist Albert Fleury wrote in 1900, “the sky is of iron, and perpetually growls a rolling thunder.”

The Loop elevated — a decidedly unglamorous, rectangular bridge of riveted steel and wood ties that’s 2.1 miles long and rises about 20 feet above Lake, Van Buren and Wells streets and Wabash Avenue — is unavoidable and underappreciated, though not by film directors who love to use it as a gritty backdrop.

It falls to Chicago Tribune book critic Blair Kamin to elaborate.

I dove eagerly into a new book, “The Loop: The ‘L’ Tracks That Shaped and Saved Chicago” (Southern Illinois University Press, paperback, $26.95, 312 pages), due out Nov. 26. Its author, the award-winning former Tribune urban affairs writer Patrick T. Reardon, makes a bold claim: “The elevated Loop — disregarded, denigrated and often unloved for much of a century — has been the single most important structure in the history of Chicago.”

It's likely there was more at work than the provision of rapid transit in those land values going up.

The elevated structure drove up real estate values within the five-by-seven block area it enclosed. It helped unify a city divided into North, South and West sides, and further subdivided into enclaves based on race, ethnicity and economic class. With its pulsating medley of offices, shops, restaurants, theaters and other attractions, the Loop became everybody’s “second neighborhood." It was a citadel of commerce, one that did not crumble during the suburban flight of the 1950s and 1960s — battered yes, but still too big and too important to fail.

The review makes a few allusions to cable cars, both in San Francisco and in the city that once had the country's biggest cable car network. It concludes with an observation that Cold Spring Shops frequently makes.

The tracks themselves are a reminder that the often-bandied about term, “infrastructure,” should mean more than the vehicle-friendly roads and bridges that politicians invariably mention when they use that term. Transit systems like today’s electricity-powered “L” move thousands of people using far less energy than all those idling pollution-belching cars and trucks on congested roads. The elevated, in other words, was green before green was cool.

Rent-seeking, however, never goes out of fashion. "If the book has a hero, it’s Charles Yerkes, the shrewd, bribe-dispensing Gilded Age streetcar magnate who masterminded the construction of the Loop elevated, which opened in 1897."