Rosenthal is now 66 and moved to Greenwood Village, Colorado, about 10 years ago to live near his grown children and grandchildren. He declined to disclose how much Panera stock he holds, but said he has invested most of his money in his expanding franchise empire.

“I always felt if I could make one store happen that I could hope or expect to have a number of stores,” Rosenthal said of his early days forming St. Louis Bread Co. “But whether that was going to be a half dozen or a dozen, I didn’t know. I was worried about opening the doors the next morning. I never envisioned it becoming quite this large.”

Along the way, Panera has been a key player in establishing the fast-casual category, generally defined as that niche between fast food and casual dining.

“Fast casual has grown a lot over the past five to 10 years, and Panera Bread is a prime example,” said Bob Sandelman, founder and president of restaurant market research firm Sandelman & Associates Inc. of Villa Park, California.

The firm’s annual customer-satisfaction and quality survey rated Panera fifth overall in the restaurant industry in 2008 and highest among fast-casual eateries. “Panera has been especially popular in the past couple of years due to the economy as people trade down from casual dining and still get quality food and a pleasant environment. In most markets, they don’t have any direct competitors with the menu items they offer. I don’t see why it wouldn’t have legs for a lot longer.”

Panera also can attribute some of its success to evolution. The company has modified its menu, updated its cafe designs and added features such as free WiFi access for laptop and smartphone users in its effort to remain current.

“Even from the beginning at the first location, we would have little groups of people who would meet there,” Rosenthal said. “It was a gathering place then, and it has become an even more significant gathering place today.”