Android is now the most-used smartphone operating system in the United States — a stunning race to the top from a platform that didn’t exist just 27 months ago.

Nearly one third, or 31.2%, of U.S. smartphones ran Google’s Android OS in January, according to a study released Monday by comScore. That outpaced the 30.4% of American smartphone owners who use BlackBerry devices, which are made by Research in Motion.

The meteoric rise of Android began in late October 2008, when HTC’s G1 phone went on sale for T-Mobile users. The platform really started to take off when the Motorola Droid went on sale in November 2009. Google’s mobile OS began 2010 with just a 7% share of the smartphone market, but Android has grown by an astounding two percentage points each month since, on average.

Android was in fourth place as recently as May 2010, but it outpaced Microsoft’s Windows Mobile in June. In November, Android overtook Apple’s iOS, which runs on the iPhone, iPod Touch and iPad. It finally conquered the mighty BlackBerry OS in the first month of this year — vanquishing an operating system that had more than a 42% share of the U.S. smartphone market a year ago.

Now, 350,000 Android devices are activated each day, and there are more than 170 smartphones and tablets running Android, according to the search giant.

Much of Android’s success can be chalked up to Google’s open business model: Google licenses the mobile OS for free, allowing handset manufacturers to load the ready-made software onto their phones instead of paying a team of engineers to develop a proprietary platform. They can customize it as much as they like, too.

(Source: CNN Money)