* Jan. 9, 2007 Apple CEO Steve Jobs unveils the iPhone during his keynote address at the Macworld conference.
* June 29, 2007 The iPhone goes on sale. Sales are limited to two phones per customer.
* Sept. 10, 2007 Apple sells the 1 millionth iPhone, 74 days after launch.
* July 11, 2008 Apple releases the second-generation iPhone, the iPhone 3G, and launches the App Store.
* July 13, 2008 The 1 millionth iPhone 3G is sold, and the 10 millionth title is downloaded from the App Store.
* Sept. 9, 2008 The 100 millionth app is downloaded from the App Store, which then contains "more than 3,000" titles.
* April 24, 2009 The 1 billionth app is downloaded from the App Store, which contains 35,000 titles.
* June 19, 2009 The third-generation iPhone, the iPhone 3GS, launches.
* Nov. 4, 2009 The App Store library grows to 100,000 titles.
* June 24, 2010 The fourth-generation iPhone, the iPhone 4, is released, selling 1.7 million units in three days.
* Jan. 22, 2011 The 10 billionth app is downloaded from the App Store, which contains 350,000 titles.
* April 27, 2011 The first white iPhone arrives, 10 months late due to manufacturing difficulties.
* July 7, 2011 The 15 billionth app is downloaded from the App Store, which contains 425,000 titles.
* Oct. 4, 2011 Apple announces the latest-generation iPhone, the iPhone 4S, generating 1 million preorders in the first 24 hours.
* Oct. 14, 2011 The iPhone 4S becomes available, selling 4 million units in three days. The App Store contains more than 500,000 titles and has charted more than 18 billion downloads.
* Release date: June 27, 2007.
* Price without contract: $500-$600.
* Colors: Black.
* CPU: 620 megahertz single-core.
* Camera(s): Rear-facing 2 megapixel.
* Storage capacity: 4/8 gigabytes (a 16-gigabyte model was released Feb. 5, 2008).
* Memory: 128 megabytes.
* Display resolution: 163 dots per inch.
* Release date: Oct. 14, 2011.
* Price without contract: $650-$850.
* Colors: Black and white.
* CPU: 800 megahertz dual-core.
* Camera(s): Front-facing 0.3 megapixel/rear-facing 8 megapixel.
* Storage capacity: 16/32/64 gigabytes.
* Memory: 512 megabytes.
* Display resolution: 325 dots per inch.
During his keynote address at the Macworld conference on Jan. 9, 2007, Apple CEO Steve Jobs answered months of rumors about the company's latest project with a bold statement and an even bolder promise.
"Every once in a while, a product comes along and changes everything," Jobs began. "Today, we're introducing three revolutionary products of this class.
"The first one is a widescreen iPod with touch controls. The second is a revolutionary mobile phone. And the third is a breakthrough Internet communications device."
And then, Jobs reached the punchline.
"These are not three separate devices. This is one device, and we're calling it iPhone."
Five years after its unveiling, the iPhone has become a household name with latter versions displaying vastly improved functionality. In the months following its announcement and subsequent release, however, Apple devotees said interacting with the original iPhone was like touching the future.
"We weren't supposed to have this stuff until 'Star Trek' time, which is the 23rd century," said Steven Disbrow, an iPhone app developer, author and president of the Chattanooga computer consulting firm EGO Systems Inc.
The iPhone's versatility and intuitiveness changed people's expectations about ttheir smartphones and other personal electronics, Disbrow added.
"If you can put the future in this little box -- which is what they've done -- then other people should be able to, too," he said. "No one will be truly happy until we have flying cars and jet packs, but this is pretty amazing stuff."
A new standard
Many of the iPhone's most innovative functions, such as a capacitive touchscreen, single-button interface and desktop-quality Web browsing, now are standard on many devices. In 2007, however, the iPhone's features set it apart from other smartphones, such the Palm Treo, Motorola Q and Nokia E61, which used physical keyboards and offered a limited Web-browsing experience.
Many heralded the iPhone as a success before it was even released.
During Jobs' Macworld address, he was joined onstage by Eric Schmidt, then a chief executive at Google. Although Google later co-developed the Android mobile operating system, Apple's primary competitor in the smartphone market, Schmidt praised the iPhone.
"Steve, my congratulations to you," he said. "This product is going to be hot."
Time Magazine named the iPhone the Invention of the Year in 2007, and adoration for the device among the Apple faithful was so high preceding its release on June 27, 2007, that many bloggers dubbed it "the Jesus phone."
By the standard of later iterations of the device, however, the iPhone moved off shelves at an almost glacial pace.
According to Apple sales data, it took more than 10 weeks to sell the first million iPhones, a figure the latest iteration, the iPhone 4S, achieved through advance orders alone in less than 24 hours preceding its release on Oct. 14.
The possibilities of the iPhone, as demonstrated during Jobs' 90-minute walk-through of the device, were so tantalizing that Disbrow said he stood in line to buy one when they went on sale on June 29, 2007.
When they were actually able put finger to screen, many were awed by the experience, Disbrow said.
"Nobody could believe that it actually did the things they saw in the commercials," he said. "When they were advertising the device, they just showed people using it.
"I remember people being amazed that I handed it to them and they knew how to use it right away, not just from their own intuition but from the commercials."
Excitement for the iPhone isn't limited to the United States.
When the iPhone 4S was set to go on sale in China on Jan. 13, Apple employees in Beijing became concerned by the size of the crowd and kept the store closed. According to reports by online news site Mashable.com, fights then broke out.
Apple has since suspended iPhone sales in China indefinitely.
'One more thing'
Despite near universal praise for its innovations, the first iPhone wasn't without its detractors. Critics decried its high price ($499 for the base 4-gigabyte model), lack of 3G connectivity and service that was initially limited to Cingular, now AT&T.
Many of these issues have been mitigated in recent years as subsequent generations have released, beginning with the iPhone 3G on July 11, 2008.
The second-generation iPhone addressed many of the original's shortcomings, including offering 3G service and third-party applications through the App Store.
Similar to almost all smartphones, the original iPhone only offered access to applications released through Apple. The release of a software development kit simultaneously with the iPhone 3G had a dramatic affect on the smartphone landscape, said Lee Walker, owner of the Chattanooga mobile/Web development firm Code Journeymen.
"The barrier to entry [as a developer] went from skyscraper to pebble overnight," Walker said. "That has been a very, very big thing.
"One of the things it does is allow you to come up with ideas for things, go through them and try them out, basically throw them at the wall and see what sticks. That quick iteration of ideas and exchange of things -- you couldn't do that before the iPhone."
Since its launch, the App Store has grown at an exponential rate. Within three days, 10 million apps had been downloaded. In less than 10 months, 1 billion had been downloaded. The 10 billionth app was downloaded last January. As of May 2011, the App Store contained more than 500,000 titles.
That success is a prime example of the value of Apple listening to its customers, Walker said.
"The people who are successful are the people who do that," he said. "Apple released the iPhone, and people said, 'We want applications for it,' so they said, 'OK' and released the software development kit.
"They're very forward-thinking, listening to what customers want."
In some ways, the iPhone's versatility has expanded what its users want, turning activities such as receiving real-time driving directions and mobile access to social networks into habitual activities.
Gaming, in particular, has grown immensely in popularity. According to Apple's website, there are more than 100,000 games available in the App Store. As of Wednesday, 40 of the top 50 highest-grossing iPhone apps are games.
Taking the plunge
Whit Gardner said she admired the iPhone for years but didn't feel compelled to buy one until last October.
When it was time to renew her contract, Gardener, 25, said the salesperson pointed out that if she chose not to purchase a smartphone, she would effectively be voluntarily placing herself behind the curve. It was all the incentive she needed to buy an iPhone 4.
Even five years after she first saw the iPhone, Gardner said the experience of using an iPhone is awe-inspiring.
"Over Christmas, I was 700 miles away from my significant other, and we could FaceTime," she said. "It sounds kind of Luddite-esque to say, 'I can't believe I'm doing this with you 700 miles away on my phone,' but when you think of how far we've come in the last five years with the iPhone and have devices that can do that stuff, it's just a powerful tool.
"I could go back, but I don't want to."