As the roar begins, Chicagoans drop their conversations. Children press their mittens to their ears with nonchalance. Neighborhood dogs quit barking.
Then comes the silver blur, the flash of sparks, and the odor of hot steel. Window panes rattle and a dusty wind blows by. Then it's over. Life resumes.
For more than a century now, Chicago's elevated railroad has helped define this city. Its thundering trains and miles of iron girders tell the story of a restless populace to whom beauty and utility might as well be synonyms.
This year marks the 100th birthday of the "L," and in many ways, of modern Chicago itself. Although ridership has fallen for 70 years and the system continues to lose money, it's nearly impossible to discuss Chicago's growth without referring to its rail maps.
Critics call it outdated, developers yearn to bury it, and newcomers curse its ceaseless rumble. But for the moment at least, most Chicagoans believe the most dreadful sound that could ever emanate from these elevated platforms would be none at all.
"Once the elevated trains were built, they were immediately taken for granted," says Bruce Moffat, author of a history of the L. "They became part of the urban fabric."
With 224 miles of track, Chicago's L is the nation's second largest metropolitan rail-transit system. Yet unlike its counterparts in New York, Philadelphia, and Boston, the majority of Chicago's tracks remain above street level.
THE city's first elevated train, a steam-powered job with brass rails and mahogany panels, began operating on the city's south side in 1892. In subsequent years, a handful of separate lines opened up with tracks that ran from the city's outskirts to points near downtown. In the fall of 1897, workers connected these stations with a 2-mile girdle.
This "loop," which eventually gave Chicago's downtown its nickname, was no less impressive a technological feat than a political one. According to Mr. Moffat, developers had to "literally bribe their way down the street," to get consent from area business owners. Even today, he notes, sudden twists and turns on outbound lines reflect long-ago refusals by property owners.
The system was an instant success. The loop allowed more workers to settle in outlying areas. Shoppers flocked to department stores like Marshall Field's through platform entrances, and downtown sweatshops gave way to jewelry stores. Tickets cost just five cents.
"It was really a major innovation for insuring the economic and commercial vitality of the downtown area," says Chicago Transit Authority (CTA) spokesman Jeff Stern. "Up until that time, people had to rely on street transportation to get downtown. The congestion was really unbelievable."
Throughout the late 19th century, Chicago grew by 600,000 inhabitants each decade. The disparate rail companies merged to form the Chicago Elevated Railroads, and extensions were built through former farmlands. New neighborhoods popped up in every direction. By 1926, downtown trains ran every 15 seconds during rush hour, and carried almost 230 million passengers.
Since then, ridership and profitability have declined steadily. After the railroad went bankrupt in 1932, city officials formed the CTA, which assumed control of the L in 1947. Today, the CTA relies on government subsidies.
Despite numerous extensions, and service to both Chicago airports, ridership in 1996 did not exceed 142 million passengers. According to Stern, the L only accounts for 20 percent of the city's mass transit now. Buses handle the rest.
Nevertheless, the viability of the L remains inextricably linked to the city's neighborhoods and its downtown business climate. A burst of urban development near the loop, Moffat notes, has boosted ridership in some areas and developers continue to build new homes within yards of the tracks.
At a recent ceremony marking the loop centennial, CTA officials offered free rides on vintage trains. In the days since those ornate cars roamed the rails, Moffat says, the factory workers who once packed them have been replaced by professionals and downtown service workers. Today's trains are quieter, sleeker, and air conditioned, he adds.
But that's about it.
"When these tracks were built, no one worried about how long they would be there, they just figured the trains would go on indefinitely," Moffat says. "They could be right."