The original Bob's Big Boy restaurant, which opened 51 years ago in Glendale as a 10-seat diner and, among other items of cultural significance, is credited with introducing double-deck hamburgers to Southern California, served its last Big Boy Combo on Monday and is now awaiting demolition.

It will be replaced by a mini-mall.

"I feel perfectly lousy about it," said Robert C. Wian, 75, who half a century ago sold his car for $350 to buy a tiny diner on Colorado Boulevard. A few years later, he converted it into a drive-in restaurant, offering cheeseburgers, French fries and shakes "so thick you can eat them with a spoon."

The formula was a success, of course. Wian eventually expanded his business into a national restaurant chain and, along the way, inspired numerous imitations. In 1967, he sold the chain to the Marriott Corp and, citing lackluster sales, it decided six months ago to sell the original Glendale property to a shopping center developer.

"There is a lot of sentiment tied up in that place," Wian said. "But it's difficult to stand in the way of progress."

The imminent demise came as sad news to those Southern Californians who revere drive-ins and double-deck cheeseburgers as part of the region's cultural heritage, and packs of people converged on the restaurant Sunday and Monday to pay their respects.

Ben Trigg was there on Sunday, just as he had been there when Bob's opened in 1938, a hungry 7-year-old whose mother rewarded him with a hamburger and chocolate shake after clarinet lessons. And just as he had been there in 1951, when it was the "hottest place in town" after Glendale High football games. And just as he has been nearly every day since.

"I hate to see it go," said the 57-year-old Trigg. "I've eaten thousands of hamburgers here. I've come here all my life."

"Hey, I grew up at this place," said Rodney Herrick, 41. "I used to come here in my battleship-gray Plymouth, order a Coke and fries and wait for girls. Hard to believe it's closing down. This place is a landmark."

When Bill Zabala, 42, heard that the place was closing he decided to take his family in "for the history value of it. I wanted them to see it before it's torn down."

And so on. The mourning took on the form of ritual, as customers slipped into the brown vinyl upholstered booths and ordered their last Big Boy Combo--a double cheeseburger, fries and a small salad drenched in blue cheese or thousand island dressing.