The conventional wisdom on Wall Street is that every bank, in some scenario, is a takeover target.

With big premiums being paid to sellers, and even a few improbable whispers about J.P. Morgan & Co. as a buyout candidate, it is understandable why most bankers are reluctant to flat-out insist that their companies are not for sale.

But that is just what the chief executive officers of the two biggest banking companies in Salt Lake City are doing.

"We're not for sale," said Spencer F. Eccles, chairman of First Security Corp., the bigger of the two. "It would take a hostile tender offer."

"Everyone is for sale at some price; that's how our system works," said Harris H. Simmons, president of Zions Bancorp. "But we are not for sale."

First Security and Zions both possess an unusual mix of performance, independent-mindedness, and other factors that fortify them against potential takeovers more than many companies of similar size.

Their returns to shareholders are extraordinarily high. They are pursuing their own expansion strategies through acquisitions in attractive markets such as California. They have long family traditions of running Salt Lake City's banks. And they benefit from tight links with local businesses and the Church of Jesus Christ of Latter Day Saints.

Gerard Cassidy, bank analyst at Tucker Anthony, and investment bankers familiar with Zions and First Security contend that their close ties to the Mormon church discourage either one from being bought out. If one were to sell to an outsider, then the close-knit community of depositors and business owners would take their money to the other bank.

"I don't think the Utah banks will ever sell," Mr. Cassidy said.

"It's like an Italian barber in New York who at the turn of the century put his money in an Italian bank," he said. "Why not keep your money with someone you have some connection to, if you can?"

Both Salt Lake banking chiefs bristle at the notion that their Mormon ties are the keys to continued independence. They emphasize business performance, and investors have no reason to complain about that.

First Security's shares rose an 87% in value last year, double the rate of appreciation in the Standard & Poor's bank index. Zions stock climbed 76%. The market value of First Security rose to $5 billion, Zions to $3 billion.

First Security, which has $17.3 billion of assets, and Zions, which has $9.5 billion, have prospered while competing with megabanks such as Wells Fargo & Co., KeyCorp, Banc One Corp., U.S. Bancorp, and Washington Mutual Inc., all of which have moved into Utah in recent years.

First Security has held on to a 28% and Zions a 20% market share in the state. KeyCorp, which bought its way into Utah in 1987, is a distant third, at 6.5%.

Meanwhile, the Salt Lake City banks have grown outside Utah, concentrating on acquiring community banks throughout the Rocky Mountain region and into California.

Both have acquired banks in Las Vegas, the nation's fastest-growing city. Zions has a foothold in California through its acquisition of GB Bancorp. of San Diego, and First Security announced last Thursday that it would acquire California State Bank of West Covina, in the Los Angeles area, for about $300 million.

"These guys aren't sellers, they're players," said James J. McDermott Jr., chairman and chief executive officer of Keefe, Bruyette & Woods Inc., New York.

Both banks give the companies they acquire a high degree of autonomy. Zions often lets its acquired units retain their old names.

"Banking is a local business," Mr. Simmons said. "Relationships are important, especially in the kinds of lending where there is still margin left."

The Utah banks also have tried to develop fee-generating businesses. First Security has had federal approval to underwrite insurance since 1931, and Zions recently won approval to underwrite municipal revenue bonds. Zions also established a subsidiary that offers digital signatures, a means of confirming the identity of customers and organizations doing business on the Internet.

But all this aside, a big reason for these banks' resoluteness about independence is that they retain the traits of family-run businesses.

Zions traces its ancestry to a bank founded by Brigham Young in 1873. The Mormon church itself owned a majority of the bank until 1960, when it sold its interest to Harris Simmons' father, Roy Simmons. The Simmons family still owns about 8%.

The younger Mr. Simmons, 42, said he "remember(s) my father telling me that he took money from people and gave it to others, and I was horrified. I thought he would get into trouble.

"Later on, my tutoring became more sophisticated."

First Security's own traditions are embodied in the Eccles clan. The family co-founded First Security in 1928, and Spencer's uncle, Marriner S. Eccles, was chairman of the Federal Reserve Board in the Franklin Roosevelt administration.

Another uncle, George S. Eccles, succeeded Marriner at First Security and served as CEO for 37 years.

But in this day and age, no company seems invincible.

The possible chink in Zions' armor is expenses-its efficiency ratio in fourth quarter, 63.5%, is lofty by regional banking standards, in part due to the company's decentralized structure.

Thomas H. Hanley, analyst at UBS Securities, says Zions could be worth $55 a share in a takeover, with cost savings to be realized from paring its expenses.

Zions closed trading Friday at $43.25. First Security closed at $35.

At First Security, the line of Eccles succession may end at Spencer's retirement. His son, an assistant coach of the U.S. Ski Team, appears uninterested in banking.

But Mr. Eccles, 62, scoffs at the notion that he may soon leave the scene. He noted that Marriner was with the bank until he was 88, George until he was 82.

"In order to have a succession issue, you must have an opening," he said, "I'm not going anywhere."

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