Of the 72.5 million smartphones in use in the U.S. in the first quarter, 34.7% were Android devices, the market research company said. Android-based smartphones accounted for 28.7% of the market at the end of the fourth quarter in 2010, when 63.2 million smartphones were in use.
BlackBerry's share of the smartphone market dropped from a 31.6% at the end of 2010 to 27.1% at the end of March, ComScore said.
Apple's iPhone saw its share of the market increase slightly, from 25% in 2010's fourth quarter to 25.5% in the first quarter of 2011.
Meanwhile, the market share for devices running Microsoft's new Windows Phone 7 and older Windows Mobile systems dropped 0.9 percentage points, from 8.4% in December to 7.5% in March. The market share of Palm devices running the WebOS operating system, now available through Hewlett-Packard, dropped from 3.7% to 2.8% quarter to quarter.
The ComScore report is based on surveys of 30,000 U.S. mobile subscribers. ComScore reports have consistently shown that the U.S. market is different from the rest of the globe, where Nokia dominates.
ComScore said Android benefits from the fact that it is supported by several smartphone makers.
Samsung (which makes smartphones running Android and other platforms) was the top
smartphone manufacturer, with a 24.5% share of the market. It was followed by LG, with 20.9%, Motorola, with 15.8%, RIM, with 8.4%, and Apple, with 7.9%.
RIM's has experienced a fairly steep decline in the past half-year; its market share has fallen more than 10 percentage points since the end of the third quarter in 2010, when its devices accounted for 37.3% of the U.S. smartphone market.
RIM last week unveiled a new operating system and two new smartphones, among other new products and services, at its BlackBerry World conference.
In another announcement at the RIM event, Microsoft CEO Steve Ballmer said that Microsoft will invest in the BlackBerry platform and will be the default provider of search and map tools for BlackBerry devices.
The RIM announcements came just a week after the company warned that its first-quarter earnings would be lower than expected and that smartphone launches would be delayed till later in 2011. The warning resulted in downgrades in RIM's stock rating by some analysts, and to a slip in RIM's stock price.
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