You probably won't be surprised to hear that Wells Fargo (NYSE:WFC) makes a lot of money. But what may surprise you is the fact that only three companies on the S&P 500 earn more than the California-based bank: Apple (NASDAQ:AAPL), Berkshire Hathaway (NYSE:BRK.A), and JPMorgan Chase (NYSE:JPM).

Wells Fargo's net income over the past 12 months adds up to $22.6 billion. That puts it right on the heels of Berkshire Hathaway and JPMorgan Chase, which earned $24.5 billion and $24.1 billion, respectively, over the same stretch. It's worth pointing out that Berkshire Hathaway is the biggest investor in Wells Fargo. The Warren Buffett-led company owns roughly 10% of the nation's third biggest bank by assets.

Apple, by contrast, has separated itself from the pack when it comes to earnings. Thanks to the popularity of the iPhone, which accounts for three-quarters of the company's revenue, Apple has generated $50.7 billion in net income over the past year. This is why Apple is the largest company in America based on market capitalization.

Wells Fargo's rank as the fourth most profitable company on the S&P 500 is notable for two reasons. The first is that the bank has only recently ascended to these heights. Prior to the financial crisis, it was a regional bank that operated, for the most part, west of the Mississippi River. At the end of 2007, for instance, it had $575 billion in assets. Flash forward to today and the figure has grown to $1.8 trillion.

A significant portion of this growth came from Wells Fargo's 2008 acquisition of Wachovia, which had run into trouble with subprime mortgages. Wachovia was larger than Wells Fargo at the time and thus doubled the latter's size.

The rest of the growth was either organic -- i.e., loan growth -- or derived from portfolio acquisitions, such as its deal last year to buy multiple loan portfolios and business lines from GE Capital. The deal included total assets of approximately $32 billion as well as businesses employing approximately 3,000 team members, according to a Wells Fargo press release.

The second reason that Wells Fargo's rank as the fourth most profitable company in America is surprising is because the bank industry is laboring right now through one of the worst interest rate environments in modern history. With short-term interest rates continuing to hover between 0.25% and 0.50%, banks are earning a fraction on their loan portfolios relative to what they would under a more normal scenario. To this end, higher rates alone could boost Wells Fargo's top line by tens of billions of dollars.

Surprising or not, Wells Fargo's place among the top-earning companies in the United States should be settling to the bank's shareholders. The more a bank earns, the better equipped it is to survive future economic downturns without permanently impairing shareholder value.