Call 'em sliders, roach burgers, gutbombs, whatever, but White Castles - those handy, dandy onion-topped burgers you "buy by the sack" - are celebrating their 70th year.

Since E.W. "Billy" Ingram and his partner Walt Anderson served the first White Castles in Wichita, Kansas, the small, square patties have become a favorite throughout the Midwest and East.

Now, two generations later, E.W. Ingram III runs this flourishing company from its headquarters in Columbus, Ohio, where it moved in 1934.

The tiny, square burgers, so popular that customers buy them by the dozens, originally sold for 5 cent each. They are a little more expensive now - as high as 39 cents in some markets. Add a dime if you want cheese.

Over the years the menu has epanded to include chicen and fish sandwiches, fries, onion rings and a kiddie meal. But the original burger remains the big seller.

The secret for success? It could be the way the five-hole burgers are cooked.

First, a layer of chopped onions and water is ladeled onto the griddle. Then, 36 frozen burger patties are put on and each is topped with a square bun. As the water heats and steam rises throught he five holdes int he burger, the meat cooks and the buns are steamed. The burger never needs to be flipped.

When cooked, the patties are placed on the other halves of the bun by spatula. Unless requested otherwise, a pickle is added.

If there is any variation, it is in the choice of condiments.

"Some people like mustand, and some like horseradish, it usually depends on the region, and what the customers are used to," says Chris Thomas, the director of marketing for White Castle Systems Inc.

The private owned chain now has 250 restaurants, with more than $291 million in sales in 1990.

Tales of the White Castle faithful are legion.

There's Douglas Redmond - who waited in line 12 hours to be the first customer whent he first White Castle opened in Joliet, Illinois - ordered 1,550 of the little square sliders for himself and his co-workers a the First National Bank. The company was so taken by this event - and others that are similar - that they include them in their promotional literature.

"They have an incredibly distinctive taste," says Mike Cull, an employee at the Ohio Department of Transportation. "They stay with you a long time."

Each year White Castle tries to expand by 20 new restaurants, outlets owned by the company.

The latest target is Philadelphia, where White Castle has three new locations. "All of the expansion is self-financed," says Thomas, "so it has to be cautious." But the management has been anything but conservative. As the pioneer of quick-serve hamburgers, E.W. Ingram helped engineer as series of firsts:

• The first fast-food hamburger chain.
• The first industrial strength spatula.
• The first heat-resistant paper cartons.

And when the management found people were buying the famous burgers in bulk and freezing them at home, they decied to package and freeze White Castle burgers for sale in selected grocery stores.