(FORTUNE Magazine) – Leon Leonwood Bean, that taciturn merchant from Maine, would have shuddered at being called trendy. But he was the standard-bearer for the 24-hour economy--nonstop commerce by and for those who can't pack it all into the daytime. Maine hunters and fishermen always knew they could count on L.L. if at 4 a.m. they needed long underwear, or a warm cap, or a pair of his famous rubber-bottomed boots. They'd give the sleigh bells on his front door a yank, and he'd roll out of bed to make a sale. Today, L.L. Bean is a billion-dollar-a-year operation that does nearly 40% of its business after hours.

No longer does the night belong to prowlers, insomniacs, and autoworkers on the graveyard shift. Chances are, it belongs to you. Here's why: An astonishing two-thirds of all American workers--over 75 million people--put in anything but traditional hours. Rather, they clock more than half their workday outside Ward Cleaver's time zone, the one that starts after breakfast and ends before supper, Monday through Friday. That's the big surprise in a new analysis of government data by University of Maryland sociologist Harriet Presser.

From big-name financial service outfits to no-name repair shops, businesses are responding to a collective impatience--to a country full of anglers who know that the bass bite best in the dark. Increasingly, the attitude is, "If I'm up, why aren't you?" Working parents want to do their banking, buying, and bookkeeping when it's convenient for them--after the kids go to sleep. The people who serve them, in turn, want to eat and shop at their convenience. And folks who work the late shift want to take care of some household chores on the way home. That they can do, in any of 319 Walgreen drugstores, 410 Safeway supermarkets, and 291 Wal-Marts open all night around the country.

Unwinding late at night with a round of golf is a bigger challenge. But Heartland Golf Park in Deer Park, Long Island, will let you tee off until 3 a.m. Open only since May, Heartland frequently has a 2 1/2-hour wait at midnight. "We've got lawyers playing with plumbers playing with factory workers," says David Wolkoff, 28, who built the course with his father and brother. "Some people come off work at midnight, and others want to play a few holes before they head for the office."

Slicers needn't worry about losing balls in the dark. As Wolkoff says, "The place is lit up like Shea Stadium." But the 24-hour economy is not without its dangers, even on a golf course. Heartland is so bright that the Federal Aviation Administration is concerned that planes with faulty instruments might mistake it for nearby MacArthur Airport. Says Wolkoff: "The FAA told us they'll let us know if we need to run for cover."

Manufacturing companies in everything from autos to steel to Cheerios have had multiple shifts for years, in part because it's cheaper to keep plants operating continuously than to shut them down and start them up again. The real growth in round-the-clock operations has been in the service sector. Like a long row of dominoes, one 24-hour service pushes against another and forces it to fall in line. If you can get a taco at 3 a.m., there'd better be a drugstore nearby where you can buy Alka-Seltzer at 3:45. And if you're stuck working on a holiday, you don't want to be stranded without your support systems. "I was in the Denver airport on Christmas Day and wondered if my insurance would cover a rental car," says William Lewis, head of McKinsey & Co.'s Global Institute, which analyzes economic trends. "I called Geico, and an agent gave me the go-ahead."

Companies that don't take the 24-hour initiative may find the choice taken out of their hands: Consumers are beginning to expect no less. If you can't fix my computer at 2 a.m., fine. I'll find someone who will. Anne Applebaum, a journalist on assignment in New York, ran into trouble one Friday at 8 p.m. when her computer broke down just as she was preparing to file a story to London. PC Computer Doctor, a repair shop, picked up the machine, fixed it within hours, and gave a 90-day guarantee. You won't find that kind of service in London--or anywhere else in Europe, where hours tend to be short, lunches long, and weekends inviolable. Says Applebaum: "All the so-called 24-hour companies tell you to call back on Monday."

The economy that never stops has its downside. "Left to its own devices, this is a trend that could eat you alive," says Morgan Stanley's chief economist, Stephen Roach, who gets frequent middle-of-the-night phone calls. It can also lead to some big mistakes. "When you're tired, vats boil over and tools drop into machines," says Martin Moore-Ede, a physiology professor at Harvard medical school and director of the Institute for Circadian Physiology in Cambridge, Massachusetts. Indeed, some of the world's worst industrial disasters have occurred at night, including those at Chernobyl, Bhopal, and the Exxon Valdez oil spill. Moore-Ede estimates that the costs of fatigue--from accidents to lost productivity--add up to a staggering $80 billion a year.

Relationships suffer. Children whose parents work odd hours must make hard adjustments at tender ages (see box). Adults on the second or third shift often find they are totally out of sync. "I'm the one leaving the party when everyone else is arriving," says Janet Mirasola, 37, managing director of Birch Brokerage Co. in Holmdel, New Jersey. Mirasola, a Brit, still lives on London time because she trades copper, aluminum, and other base metals that are most active on the London exchange. Her workday begins at 2 a.m., when she straggles into her home office, chats with her Asian clients, and settles down to four hours of trading. At 6 a.m. she drives ten minutes to her firm's office. By noon, she calls it a day. Before she goes to bed at 7 p.m., she likes to exercise, do a little shopping, and have dinner with her husband. The dinner part can be tough: As chief financial officer of Birch Brokerage, Michael Mirasola keeps traditional hours. Says his wife: "I'm forever calling and saying, 'When are you coming home?' "

Indifferent markets--and some convincing economics--leave men and women no choice but to cope. Just how much extra business can a 24-hour operation attract? Companies that pioneer the night for their industries often find the gains to be prodigious. But International Data Corp., a research firm in Framingham, Massachusetts, says even companies trying to catch the trendsetters can add 5% to revenues--no small change in these growth-starved times. "You have to assume that some of the business done at 4 a.m. would have been done during the day," says McKinsey's Lewis. "But not all of it."

International Data Corp. estimates that more than 40% of large U.S. companies work under the stars, at least in some aspects of their business. And that's just the beginning, says Bruce Marlow, chief operating officer of Progressive Corp., the Cleveland auto insurer that is a 24-hour trailblazer: "You're talking about a tidal wave that will roll through every one of our service and distribution industries." As the folks at CNN say, it's always prime time somewhere.

Kinko's Inc., a privately held chain of copy shops, moved to a 24-hour schedule when people literally started banging on its windows after hours. "Sometimes we'd be working overtime to finish a project, and people would pass by and see the lights on," says Greg Melheim, president of Kinko's of Illinois. "They started knocking on the glass, begging us to let them in. 'Please, please,' they'd say, 'can I just make five copies?' "

Peer into Kinko's, and you see the 24-hour world at work. The company's 803 stores around the country are magnets for ambassadors of the night: everyone from dreamers pursuing secret schemes and second careers to executives putting the final touches on tomorrow's presentation. "A police officer on the night beat always comes in on his breaks to use our printers," says Jim Chapman, a Kinko's employee in Kansas City. "Turns out he's a comic book illustrator on the side."Another of Chapman's regulars runs a hotel shoeshine. He breezes by around 5 a.m. to run off fliers that read FAST EDDIE, THE BEST SHOESHINE IN TOWN.

In Chicago, Kinko's has hooked into a different dimension of the 24-hour economy by opening an office in the lobby of the Stouffer Renaissance hotel, a favorite spot of foreign executives. Explains the hotel's general manager, John Bruns: "Our customers were coming down at odd hours asking us to fax things abroad and help them with their desktop publishing. We weren't equipped to meet their needs." So last Christmas, Stouffer and Kinko's began collaborating; now business is booming, Melheim says. "The hotel guests love it because their bodies are running on a different clock, and we're in sync with them."

Except for what's stowed under people's mattresses, money doesn't sleep anymore, and neither does the financial services industry (see box). Somewhere around the world, markets are open. George Milling-Stanley, a precious-metals analyst for Lehman Brothers in New York, remembers what he did when war broke out in the Gulf. "I was sitting down to dinner in Chinatown with some friends. Just as the food arrived, we heard that planes were on their way to Baghdad. We got the check, took doggie bags back to the trading desk, and worked well into the night."

Banks have long since given up bankers' hours, what with the strange lives their customers lead. It used to be that ATMs and automated voices handled the after-hours crowd. Now many banks are adding warm bodies around the clock who provide much more than basic account information. A leader is Huntington Bancshares in Columbus, Ohio. If in perusing the newspaper late at night you see an ad for the car of your dreams, call a Huntington loan officer. She'll tell you within ten minutes whether you should dream on. Huntington books 10% of its loans in off hours. Boston's BayBanks has distributed a 53-page catalogue that lets after-hours customers choose services ranging from a safe deposit box (catalogue No. SP-2301) to a $1,000 credit line and overdraft protection (No. CL-2301). Business generated by its 24-hour number (800-BAY-FAST) equals that of 30 full-service branches.

The economics of running a business nonstop are elementary--and utterly compelling. As David Ricci, a retail analyst at securities firm William Blair & Co., puts it: "What does it cost to keep a place open? A few heads and a little electricity." There are even hidden bargains. Pennsylvania Power & Light charges its largest industrial users about 30% less for electricity purchased after hours. And small retail outlets pay Detroit Edison only half as much in off-peak hours.

Fidelity, which was first among mutual fund companies to offer 24-hour service, says using its brick and mortar more efficiently saves millions of dollars a year in capital costs. Explains executive vice president Roger Servison: "If we held all our business to daytime hours, we'd need a lot more buildings to house the staff required to handle the calls." Servison estimates that roughly 40% of Fidelity's telephone business comes in during off-hours: "You might say that having been first, we enjoy more than our fair share of night owls."

When a company breaks the barriers of a nine-to-five world, 24 hours at full steam is hardly the only alternative. A skeleton crew may be all that's needed on the graveyard shift. And sometimes two shifts are enough to meet demand. Maintenance crews often take over for a portion of each day; Heartland Golf Park, for example, has to close for a few hours to replace divots and water the greens.

Many services can be delivered from anywhere in the world. This allows workers to quit at a reasonable hour and pass their spreadsheets to colleagues in another time zone--ideally where labor and land cost less. Why should the Citibank customer in New York know or care that his late-night query goes to a call center in Nevada--or South Dakota--as long as someone takes care of his problem?

Progressive Corp. says it has eliminated millions of dollars in waste--and doubled its market share--since leading the night charge for the auto insurance industry in 1991. As readers of FORTUNE's recent story (August 7) on the company and its bizarre, gifted boss may recall, a Progressive claims rep will meet policyholders on the road anytime of the day or night if they have an auto accident. The prompt response saves money because it makes policyholders less likely to hire an attorney to settle their claims. If an attorney stays out of things, a person with a lower-back or neck injury gets an average of $2,100 from the insurance company; when a lawyer is involved, the settlement averages $9,400. That's because someone who has legal representation tends to see more doctors who recommend more medical procedures. An independent study done by the Insurance Research Council shows that after paying their doctor and lawyer fees, policyholders who hire an attorney pocket an average of $100 less than those who don't. The upshot: The number of Progressive's accident victims who use an attorney has declined 20%.

The good will generated by continuous service is harder to measure than the profits. But L.L. Bean, for one, has built the business on it. To this day, nocturnal outdoorsmen fearful of being caught in a storm are welcome to sleep in tents set up for sale on the showroom floor. The payoff comes next morning, when the indoor campers stock up on supplies before heading out again.

The biggest challenge posed by the nonstop economy may be a physiological one: how not to sleep through it. As physiologist Moore-Ede says, "We're simply not designed for this 24-hour world we've created. Our internal clocks adapted us perfectly to a world where we slept by night and hunted by day." He recommends that night workers take frequent catnaps. Kinko's Chapman agrees: "A ten-minute power nap will keep you going for hours." Connie Lehman, who sometimes works nights as CNN's director of video resources, says her solution is to maintain a well-lit, high-adrenalin environment, and then to sleep well during the day. "Put up black curtains in your room," she says. "Don't let your body know the sun is shining."

Naps may take care of our bodies. But how about our souls? What's clear in the tales of men, women, and children who have joined the army of the night is that human nature and relentless commerce are fundamentally at odds. Yes, as Progressive's Marlow says, "We can't hold back the 24-hour economy." But even God rested on Sunday. And during the winter of 1967, L.L. Bean shut down--on the day that Leon Leonwood was buried.