Remember the Googlephone? It was a mythical device that was obsessively rumored in the months after Apple launched the iPhone. Exactly five years ago today, Google unveiled the project that had been the source of all the rumors: its Android mobile operating system, along with the first Android smartphone, the T-Mobile G1. (It was also the day that Google founders Sergey Brin and Larry Page rollerbladed to the New York launch event from Grand Central Station.)

Des Smith, a member of the original Android team, remembers the launch well. "We had been working for months and months with a small team in Building 44 in Mountain View, CA," he wrote in a commemorative post on Google+. "I was so excited I couldn't sleep." The original Android team included Hiroshi Lockheimer, Keva Nelson, David Conway, Grace Kloba, Peisun Wu, Erick Tseng, German Bauer, and of course former Android chief Andy Rubin.

Read this: Android: A visual history

No one was quite sure what to expect from Google

No one was quite sure what to expect from Google that day. Most were betting that Google would release a phone, but few expected Google to reveal a mobile operating system that anyone could use. "It felt a bit like a new era for the mobile industry," The Verge's Paul Miller wrote at the time at Engadget.

The G1 has faded from memory, but Android has had a lasting impact. The open source operating system has launched more than a billion devices, including cameras, televisions, smartwatches, and game consoles. It's been a boon to the open source developer community in addition to making mobile giant Samsung rich off its popular Android-powered devices. Now, Android is the largest smartphone operating system in the world. "And this is just the beginning," Smith wrote.