On June 26, 1974, at 8:01 a.m., a clerk at Marsh's supermarket in Troy, Ohio ran a $1.39 10-pack of Wrigley's Juicy Fruit chewing gum under a UPC scanner and rang up world trade history. Time has long since taken the names of the shopper and checker. Visitors to the Smithsonian National Museum of American History, however, may see the bright yellow packs of gum on display between the Star-Spangled Banner and Alexander Bell's telephone. It was the first product with a bar code scanned at a checkout counter.

The twin technologies of bar code and scanner "allowed the retail industry tremendous flexibility and capability to price and track products," says Lois Kemp, product line director for fixed-position scanners at NCR Corporation, which installed that first stationary bar code scanner in 1974, and remains the global leader in the $300-million worldwide market."

Over a quarter century of research and development brought the chewing gum to the scanner. "Modern bar code began in 1948," describes Russ Adams, editor-in-chief of ID Systems Magazine. "Bernard Silver, a graduate student at Drexel Institute of Technology in Philadelphia, overheard the president of a local food chain asking one of the deans to undertake research to develop a system to automatically read product information during checkout. Silver told his friend Norman Joseph Woodland about the food chain president's request." The problem fascinated the pair, and, by 1952, they had built and patented a prototype system. Their invention allowed exactly 1,023 product classifications.

Today, of course, retailers ring up millions of unique universal bar codes daily on commercial systems developed in the late 1960s and standardized in the early 1970s. "The UPC label is a broad public standard so a retailer can manufacture a single product for many, many retailers," says Kemp. "Imagine Pepsi or Coke having to put different labels on their products to sell them to Wal-Mart, Kroger, or other supermarkets."

Instead, manufacturers apply to the Uniform Code Council for a six digit identification number-The Coca-Cola Company, for example, is 049000. The next five digits of the code identify individual products-00551 in the case of a two-liter Sprite bottle-and the last number is a check digit to guard against errors or fraud.

The bar code turns thirty this year, but some doubt it will see forty. Industry giants such as Wal-Mart and the Pentagon are leading a shift from UPC bar codes to smart labels, or radio frequency identification (RFID) tags. RFID tags, which first saw commercial use to track cattle, communicate automatically with electronic readers connected to larger networks of retailers and manufacturers.

All the same, Kemp insists new developments will keep bar codes competitive "long before RFID is cost-effective." She describes "very small bar codes that you can put on produce for accurate, automated pricing" and "extensions to the bar code that allow retailers and manufacturers to track expiration dates" for everything from meat and dairy to magazines and greeting cards.