Development of an Apple smartphone began in 2004, when Apple started to gather a team of 1,000 employees led by hardware engineer Tony Fadell, software engineer Scott Forstall, and design officer Jony Ive, to work on the highly confidential "Project Purple".

Then-Apple CEO Steve Jobs steered the original focus away from a tablet (which was later revisited in the form of the iPad) towards a phone. Apple created the device during a secretive collaboration with Cingular Wireless (later renamed AT&T Mobility) at the time—at an estimated development cost of US$150 million over thirty months. According to Jobs in 1998, the "i" word in "iMac" (and therefore "iPod", "iPhone" and "iPad") stands for internet, individual, instruct, inform, and inspire.

Apple rejected the "design by committee" approach that had yielded the Motorola ROKR E1, a largely unsuccessful "iTunes phone" made in collaboration with Motorola. Among other deficiencies, the ROKR E1's firmware limited storage to only 100 iTunes songs to avoid competing with Apple's iPod nano. Cingular gave Apple the liberty to develop the iPhone's hardware and software in-house, a rare practice at the time, and paid Apple a fraction of its monthly service revenue (until the iPhone 3G), in exchange for four years of exclusive U.S. sales, until 2011.

Jobs unveiled the first-generation iPhone to the public on January 9, 2007, at the Macworld 2007 convention at the Moscone Center in San Francisco. The iPhone incorporated a 3.5-inch multi-touch display with few hardware buttons, and ran the iPhone OS operating system with a touch-friendly interface, then marketed as a version of Mac OS X. It launched on June 29, 2007, at a starting price of US$499 in the United States, and required a two-year contract with AT&T.


Worldwide iPhone availability:
  iPhone available since its original release
  iPhone available since the release of iPhone 3G
On July 11, 2008, at Apple's Worldwide Developers Conference (WWDC) 2008, Apple announced the iPhone 3G, and expanded its launch-day availability to twenty-two countries, and it was eventually released in 70 countries and territories. The iPhone 3G introduced faster 3G connectivity, and a lower starting price of US$199 (with a two-year AT&T contract). Its successor, the iPhone 3GS, was announced on June 8, 2009, at WWDC 2009, and introduced video recording functionality.


First iPhone on display under glass at the January 2007 Macworld show
The iPhone 4 was announced on June 7, 2010, at WWDC 2010, and introduced a redesigned body incorporating a stainless steel frame and a rear glass panel. At release, the iPhone 4 was marketed as the "world's thinnest smartphone"; it uses the Apple A4 processor, being the first iPhone to use an Apple custom-designed chip. It introduced the Retina display, having four-times the display resolution of preceding iPhones, and was the highest-resolution smartphone screen at release; a front-facing camera was also introduced, enabling video calling functionality via FaceTime.

Users of the iPhone 4 reported dropped/disconnected telephone calls when holding their phones in a certain way, and this issue was nicknamed "antennagate". In January 2011, as Apple's exclusivity agreement with AT&T was expiring, Verizon announced that they would be carrying the iPhone 4, with a model compatible with Verizon's CDMA network releasing on February 10
From the passage provided, extract the date when the iPhone was announced publicly for the first time.
Then-Apple CEO Steve Jobs publicly announced the first-generation iPhone on January 9, 2007, at the Macworld 2007 convention at the Moscone Center in San Francisco.