Updated: Steve Jobs Resigns As Apple CEO, Cook Taking Over

Apple (NSDQ: AAPL) co-founder and CEO Steve Jobs, who brought the company back from near-disaster to one of the world’s most valuable and game-changing technology organizations, has resigned. Tim Cook, Apple’s COO is taking over.

“I have always said if there ever came a day when I could no longer meet my duties and expectations as Apple’s CEO, I would be the first to let you know. Unfortunately, that day has come,” Jobs wrote in a letter released by Apple. Jobs said in the letter that he would agree to serve as chairman of the board if approved by directors — a request immediately granted.

Jobs has battled health issues since 2004, when he underwent an operation to treat a rare form of pancreatic cancer. He returned to Apple, but was forced to go on medical leave twice in recent years: first in 2009, when he eventually underwent a liver transplant operation, and earlier this year, when his leave was described as indefinite. Each time, he remained engaged with the company — usually behind the scenes, but publicly when needed.

Cook has been running Apple on a day-to-day basis since Jobs’ latest medical leave took effect. He is considered an operations genius, a huge force behind Apple’s supply-chain and component-sourcing strategies that have it currently positioned extremely well for a mobile-oriented future that Apple helped define with the launch of the iPhone in 2007.

It’s rather difficult to understate what Steve Jobs means to Apple. He has been the public face of the company ever since his return in 1997, when he oversaw the reformation of a once-proud company that was on the brink of running out of cash. Following his return to Apple after the purchase of his company NeXT, Jobs oversaw a remarkable renaissance at Apple involving digital music and mobile technology. He enforced a strict culture of secrecy and design excellence at the company, and presided over carefully choreographed introductions of new products that came to be known as “Stevenotes.”

Cook lacks Jobs’ public charisma, but in recent years other lieutenants have been taking on more and more of Jobs’ responsibilities during those keynote presentations, the most recent of which came in June at Apple’s Worldwide Developers Conference.

The most important short-term reaction to this announcement will come from Apple’s shareholders when the stock market opens tomorrow. Guessing the impact of Jobs’ departure from Apple on its market value has been a grim parlor game for many in the years since his health declined, but it will most likely be significant.

Apple closed up slightly in regular trading, but after a 30-minute halt, the stock dropped quickly in after-hour trading. It was down more than 5 percent to $357.75 just after 7 p.m. eastern, a relative blip. What matters most is how the market reacts in the morning — and where it closes tomorrow. Given the current jittery market, it could be a harsh start to the day. Then again, Apple’s stock performed quite well when Cook was in charge before, rising nearly 70 percent.

Staci adds: As it happens, I had lunch today with Alan Patricof, one of Apple’s earliest investors. (Years later, he invested in our company, too, through his Greycroft fund.) I asked Patricof to share his thoughts tonight:

“It is truly a sad moment for Apple, for the entrepreneurial community in general and for him. He has set the goal line for all of us. It seems like only yesterday that we were lucky enough to be one of the early investors when we were all much, much younger – but it is almost 30 years. Who would have dreamed how much he would achieve in 30 years! I personally wish many more years of raising the bar for us all.”