How the Apple iPhone became one of the best-selling products of all time

When Apple announced the iPhone in 2007, Steve Jobs called it a "revolutionary product" in a handset category that he said needed to be reinvented. 

Now, nearly two decades and 42 models later, the iPhone is one of the world's most popular phones. Apple has sold over 2.3 billion units of the iPhone and has over 1.5 billion active users, according to research from Demand Sage.

The original iPhone was released in June 2007 and exclusively sold with AT&T for $499. 

"Investors were optimistic about the impact that it could have with Apple," said Deepwater Asset's Gene Munster. "The initial data that came out from AT&T was a disappointment from that first few days of sales. I remember talking to investors after that first weekend, and the general sense was that this product, in one investor's words, was dead on arrival."

Apple sold 1.4 million iPhones in 2007 with 80% of the sales coming in Q4. In the same year Nokia, the maker of the iconic Nokia 3310, sold 7.4 million mobile phones in Q4 alone. 

"Nokia was seen as unstoppable, unbeatable," said CNBC technology reporter Kif Leswing.

"The investing community largely took this as something that is going to be a much more difficult market for Apple to really crack," said Munster. 

Things started to shift for Apple in 2008 when it launched the App Store. This helped spur a new wave of modern tech companies like Uber and put Apple ahead of its competitors. 

"The App Store allowed your phone to become a lot more," said Munster. "That was the piece, that insight, other phone manufacturers didn't see that coming."

Apple saw increased iPhone unit sales in the years following the App Store. The company hit a major milestone — more than 50 million units sold — in 2011, with the help of the