On this day in economic and business history...

May 15 is a historically significant day for the members of the Dow Jones Industrial Average (^DJI 0.40%). Three key events occurred on this day that helped shape three component companies you can invest in today. There was plenty of other business history made on this day as well. Let's take a look at some of these events now, for a better understanding of where these companies came from and where they might be going next.

Before the Golden Arches
The very first McDonald's (MCD -0.91%) opened on May 15, 1940. Called "McDonald's Bar-B-Que" and featuring a diverse array of different barbecued favorites, this early prototype bore little resemblance to the modern megachain that it helped create. With carhops servicing a parking lot that might sometimes crowd with 125 vehicles on the weekends, it was more a drive-in diner than a drive-through fast-food restaurant.

After several years in business, brothers Richard and Maurice McDonald realized that their best-selling and most profitable meal was a simple hamburger. They closed the restaurant for several months of retooling, reopening in December 1948 as McDonald's, in a format that would be easily recognizable to Mickey D's diners today. Since then, McDonald's has grown tremendously. Here are some of the key events in Mickey D's history that followed its 1948 retooling (click the links to read more):

Little pharma goes big
Merck's (MRK 0.37%) history on American public markets stretches back to the end of World War I, when authorities seized the U.S. subsidiary of a German chemical-maker (also named Merck) to prevent the Kaiser from profiteering off American needs. After the war, Merck was re-established as an American corporation, and it traded on over-the-counter markets until after the end of World War II. On May 15, 1946, Merck -- fresh off its earliest successes with modern pharmaceuticals -- stepped up to the New York Stock Exchange.

One share of Merck stock was worth $73.50 at the end of its first day on the NYSE. Six decades later, after a number of stock splits, that one share had grown into 1,296 shares worth nearly $50,000, not counting any of Merck's decades of potentially reinvested dividend payments.

The house of...some kind of cartoon animal
Mickey Mouse's debut is often celebrated in November to mark the release of Disney's Steamboat Willie. However, the House of Mouse's rodent mascot actually premiered on May 15, 1928, when Walt Disney gave a theater audience a private test-screening of Plane Crazy. The silent black-and-white cartoon film didn't wow the crowd enough to win Disney any distribution contracts, so he went back to the drawing board to produce the fully audio-visual Steamboat Willie, which earned the company one of its first independent cartoon success. After Steamboat Willie became a hit, Disney went back and dubbed a soundtrack onto Plane Crazy, which was released to the public in the spring of 1929.

The banks in Spain
Banco Santander (SAN 0.99%) was founded by royal decree on May 15, 1857. The bank was established from its earliest days as an international financial operation, but it was not until the 20th century that it began to swell to its presently humongous size. Between the turn of the century and the end of World War I, Santander's balance sheet doubled, and it began building out its network of branches during the interwar period. By the time Santander celebrated its centennial, it had become Spain's seventh-largest bank, but this was a modest start -- the bank's second century would bring even greater growth.

Santander expanded into Latin America beginning in the 1970s, and by the late 1980s it was also firmly established across the European continent. Santander prepared for the transition to the 21st century by completing a megamerger with Banco Central Hispano, the first such major deal after the adoption of the euro. After the financial crisis, Santander's relatively conservative management and numerous acquisitions allowed it to become the eurozone's largest bank by market value. However, Santander today sags under the same grinding recession that has put millions of Spaniards out of work and destroyed the country's economic growth. It was recently forced to write off more than $25 billion in nonperforming loans for Spanish properties. Will this venerable bank find its fortunes torpedoed by European malaise, or will Latin America be the savior that keeps Santander growing? We'll find out in due time.

The public's online store, now available to the public
Amazon.com (AMZN 3.43%) went public on May 15, 1997. The highly anticipated debut of a true dot-com-era darling saw shares close at $23.50 after underwriters raised the pre-IPO price several times, from an initial range of $12 to $14 up to $16 per share, and then to $18 per share the night before Amazon debuted on the Nasdaq exchange. By this measure, it was a solid success both for Amazon -- which didn't leave much money on the table -- and for pre-IPO buyers, who came away with a 31% gain on the day. Amazon came away with $54 million in funding and earned a market cap of $438 million for its efforts.

At the time, Amazon was coming off a quarter in which it generated $16 million in revenue and posted a loss of $3 million, with about 80,000 visitors checking the site out each day. These numbers seem positively quaint now: 15 years later, Amazon's first-quarter report showed $16.1 billion in sales (a 100,500% increase), and the e-retailer was now by far the world's favored online shopping destination, with an estimated 163 million unique daily views. Amazon bears will point to its difficulty in maintaining profitability, but that hasn't tempered the market's enthusiasm. In the 15 years since first going public, Amazon has delivered first-day shareholders an astounding 13,060% return.