70 million represents a lot of people for a country, much less for a bank’s customers. It’s nearly a quarter of the United States’ population. In fact, you could add every person in California and Texas together and still not reach the 70 million mark.

And that massive amount of customers doesn’t come to a bank by accident.

No, one bank has developed a winning strategy that it’s used to not only win a customer’s business, but keep them around for the long term. This strategy has proven so successful that the bank I’m about to tell you about now serves more households than any of its competitors.

Of course, you’d expect this sort of successful strategy to show up in a company’s share price; once again, this company hasn’t disappointed patient investors.

Despite being a major bank caught in the credit crisis, the shares have rebounded more than +200% from their 2009 lows. Today, they still trade where they were before this crisis began… but there’s a big difference between then and now that could drive the stock even higher.

During the crisis, this company made a major acquisition, and it’s now in the process of rolling out its proven strategy to a whole new group of customers.

Wells Fargo’s (NYSE: WFC) strategy is actually pretty straightforward. It strives to cross-sell its customer base multiple products, be it checking or savings accounts, home mortgages, student loans, brokerage services or credit cards.

That approach has led to high levels of client retention and is a major reason Wells boasts such a large customer count in the United States. In terms of market share, Wells is number one or two in dozens of product categories.

But remember that near the apex of the credit crunch, the bank took over struggling Wachovia and its 15 million customers. Not only did the acquisition give the bank a larger footprint (especially on the East Coast), but it also represents a larger base to cross-sell. The company estimates it can cross-sell current Wachovia customers on 30% more products to bring them in line with the average Wells Fargo customer.

And with a laser focus on cross-selling, Wells Fargo doesn’t have much need for certain activities that other banks pursue. This includes investment banking segments and proprietary trading desks, which can be fantastically profitable, but extremely volatile.

Wells recently estimated its trading assets are just 10% that of JPMorgan Chase (NYSE: JPM). They’re in the low teens of other leading investment and retail banks.

Large banks with these business units are being targeted by politicians in current financial reform legislation, which means their profit potential could be seriously dented. But Wells doesn’t have this problem.

Overall, the bank made it through the apex of the credit crisis in enviable fashion. It remained profitable on an annual basis, due primarily to the factors cited above, although return on equity (ROE) did dip below 10%.

Return on equity should eventually return to at least 15% as the economy recovers and the Wachovia customer base grows more profitable over time. A mid-teens ROE translates into about $3.33 per share in earnings, which should be achievable in the next couple of years.

Applying a conservative P/E multiple of 12 (the P/E is currently 16) leads to a stock price of $40 per share, or approximately +50% above current levels.

Action to Take –> The recent credit crunch will obviously make it very difficult for Wells Fargo to return to pre-crisis growth and profit levels, but there is ample room for improvement from where its operations stand right now. Its simple business focus makes it the safest and potentially most undervalued bank in America today.