Android has overtaken both the iPhone OS and BlackBerry for the coveted position of #1-selling US smartphone platform. An NPD study released today shows that 33% of smartphone sales in the United States are Android OS devices. RIM is now down to just 28%, while iOS has boosted up to 22%.

The original Motorola Droid lead Android smartphone sales, while the Droid Incredible and HTC Evo came in close behind. The Eris and Hero nabbed the fourth and fifth spots. A great deal of credit for the expansion of Android goes to Verizon, whose buy-one-get-one-free deals spurred a surge in Android adoption.

Next quarter may see some changes in these numbers. This data only takes into account the first few days of iPhone 4 availability. Still, it seems unlikely that a couple months worth of iPhone sales will be able to close that 11% gap. Android is likely to stay on top for quite a while.