Apple became the first American company to reach a $1 trillion valuation on Thursday, but CEO Tim Cook is downplaying the historic milestone.

"While we have much to be proud of in this achievement, it's not the most important measure of our success," he wrote in a memo to employees, first obtained by Reuters. "Financial returns are simply the result of Apple's innovation, putting our products and customers first, and always staying true to our values."

Apple's trillion-dollar market capitalization--the stock price per share multiplied by the number of outstanding shares--seems especially remarkable considering the company nearly went bankrupt in 1997, but it's not the first time a company has hit the $1 trillion mark. Chinese oil company  PetroChina reached a $1 trillion valuation in 2007 before seeing its value drop to around $260 billion during the global financial crisis of 2008.

For Cook, more important than growing your company's public market valuation to a particular level is the ability to create a world-class team committed to the success of the company.

"It's you, our team, that makes Apple great and our success is due to your hard work, dedication, and passion," Cook wrote. "I want to thank you from the bottom of my heart for all the late hours and extra trips, all the times you refuse to settle for anything less than excellence in our work together."