IN THE MID-1950S CHARLES MORTIMER, PRESIDENT OF General Foods Corporation, urged the company’s Post division to think outside the cereal box. Mortimer’s push to diversify Post’s breakfast-food offerings led to a number of culinary milestones: Brim, a breakfast-in-milk product that is now remembered mostly as the inspiration for Carnation Instant Breakfast; Tang, the powdered orange drink that the astronauts drank; and, most important, the world’s first toaster pastries.

The pastries needed to have less moisture than most fresh foods (to prevent decay at room temperature and keep the crust from getting soggy) but more than most dried ones (to make them palatable). Fortunately, General Foods had recently developed a dog food called Gaines Burgers. These could be kept on the pantry shelf indefinitely, yet they still looked and tasted plausibly like real hamburgers (to a dog, anyway). Post engineers adapted this technology for human consumption in their toaster pastries and, in so doing, helped establish intermediate-moisture foods as a new category. The dog-food-inspired technology was soon applied to military rations, and it is found in today’s supermarkets in such products as granola bars, pie crust, canned frosting, meat snack sticks, and thin-rolled fruit snacks.

In August 1963 Post began testing its toaster pastries in Seattle, Indianapolis, and Portland, and on February 16, 1964, Post Country Squares were introduced nationwide. The new product alarmed Post’s archrival, Kellogg. “My first thought was that it would be highly unlikely any youngster who had one of those for breakfast would be eating a bowl of cereal too,” recalls Bill LaMothe, then Kellogg’s vice president for product development. So Kellogg decided to make its own.

Not knowing much about pastry, Kellogg sought help from a Keebler plant with experience making fig bars. Development went fast, and on September 14,1964, Kellogg had a competitive toaster pastry called Pop-Tarts in stores. Unfortunately, adult focus groups hated them.

But Keebler’s plant manager, with the inappropriate name of Bill Post, knew that his children loved heating and eating the new pastries. Post was always bringing home cookies and crackers, which his kids “usually turned their noses up at. But they asked me to bring more of those fruit scones.” Kellogg took the hint and aimed its marketing squarely at America’s youth. To cut waste and lower costs, Kellogg eliminated Pop-Tarts’ original rounded corners, which were designed to make them look more like toast. The first Pop-Tarts were also scored along a diagonal to make them easier to break in two, but within a year the scoring was eliminated.

Kellogg won the Zeitgeist sweepstakes when the name Pop-Tarts, chosen for the way they popped out of the toaster, turned out to echo a pair of 1960s cultural movements, pop music and pop art. Post, by contrast, was stuck with Country Squares, a doubly corny name made all the worse since the Beatles had arrived in America less than two weeks before they hit the market. (Post later changed the name to Toast ’em Pop Ups.)

As a breakfast specialist, Kellogg had more riding on the success of its product than the conglomerate General Foods, and in 1972 Post abandoned the toaster-pastry business, leaving Kellogg to colonize the breakfast table with 32 flavors of Pop-Tarts at last count, along with Pastry Swirls, Snak-Stix, and even, briefly, Pop-Tarts Crunch Cereal. The huge success of Pop-Tarts caused an explosion of toaster-heated items, which now include such delicacies as cheese steaks, pizza, and scrambled eggs with bacon (all enclosed in crust, of course). In the toaster-pastry category, Pop-Tarts now account for nearly 80 percent of the $431 million Americans spend annually. And the field is still a locus for innovation, as can be seen from what may be the ultimate in mixed nutritional messages, now available in stores: organic toaster pastries.