On this day in economic and financial history...

The first days of October have been eventful for many members of the Dow Jones Industrial Average (INDEX: ^DJI). Many billions of dollars in shareholder wealth have been created as a direct result of early October's fortuitous corporate moments.

Wal-Mart (NYSE: WMT) went public at the beginning of October 1970. The "Midwest discount and variety chain" (as described by The New York Times) was unofficially eight years old at the time. It joined the New York Stock Exchange two years later, by which point its stock had already split once and it had grown to a 51-store chain with $78 million in sales.

Holding 100 Wal-Mart shares bought at the IPO through 11 stock splits would have earned you total gains of 919,000%, not including any reinvested dividends. The company's earned those gains. Its present-day revenue is nearly 6,000 times larger than it was in 1972.

At the beginning of October 1928, Standard Oil's New Jersey-based antitrust spinoff company joined the Dow. You know it today as ExxonMobil (NYSE: XOM). It has maintained its place on the index without interruption for the past 84 years.

Dow component American Express moved forward to its modern business model when it launched its first credit card this week in 1958. Today, American Express has nearly 100 million cardmembers around the world generating over $800 billion in spending each year. The company's bottom line is nearly 600 times fatter today than it was in the year following the first Amex.

JPMorgan's (NYSE: JPM) corporate ancestor began the banking dynasty that still bears his name at the beginning of October 1854. Junius Spencer Morgan, the father of John Pierpoint Morgan, became a partner at George Peabody's banking firm that year. By 1864, following Peabody's retirement, he renamed the firm J. S. Morgan & Co. The millions Junius made in merchant banking gave his son J. P. a big leg up when he created his own firm in 1871.

October's been doubly valuable to Dow component Procter & Gamble (NYSE: PG). The company first began testing its newly developed Tide detergent in October 1946. Today, the company's various laundry products account for more than a quarter of the total global fabric-care market. In 2005, Procter & Gamble began its October by welcoming Gillette into the fold. Finalizing the $57 billion acquisition created the world's largest consumer-products company, vaulting Procter & Gamble over rival Unilever in market cap, revenue, and net income.

These five companies collectively make up 19% of the Dow's present value, with a total net worth of more than a trillion dollars. That's a lot of value to create in a few short days in history, even though they were spread across many years.

JPMorgan has one of the longest unbroken chains of corporate ancestry in the world. Is it the big bank that's built to last? Or was it lucky to narrowly avoid disaster on more than one occasion? There may be one bank left standing that's earned the right to be called "the best big bank," but the Fool's analysts don't think it's JPMorgan. Find out why we think this conservative competitor will thrive for the long term in our latest free report -- just click here for the information you need, at no cost.