Investors gobble up Shake Shack

From Shake Shack's (SHAK) first days in 2004 as a modest food stand in Manhattan's Madison Square Spark, customers haven't been able to get enough of its "roadside"-style burgers. Now investors seem to have just as great a taste for the restaurant chain's shares.

Shake Shack's stock price shot up more than 131 percent on Friday, to $48.44, in the company's public market debut, valuing it at more than $1.7 billion. The company's initial public offering priced at $21 a share, raising $105 million.

When Shake Shack first opened, its promise of "fresh, simple, high-quality food at a great value" was an immediate hit with fans of an All-American meal of burger and fries. The company also showed great timing. Americans' have grown more health-conscious, with younger and more upscale customers in particular reducing their consumption of fast-food.

Shake Shack is reaping the benefits of that trend, showing fast growth. The chain now has 63 restaurants in roughly 10 states and Washington, D.C., as well as nine locations outside the U.S., including London, Istanbul and Dubai.

Shake Shack is just the latest entry into America's hot and ongoing love affair with burger chains. Despite rising beef costs this year, 9 billion burgers were ordered at U.S. restaurants and food service outlets in 2014, up 3 percent over the previous year, according to research firm The NDP Group.

Not all burger chains are thriving. Fast-food giant McDonald's (MCD), faced with mounting competition chains like Shake Shack, moved to replace its CEO this week in an effort to shore up its slumping sales, reverse its declining market share and win back disenchanted customers.