Google's mobile OS has grabbed 39 percent of the U.S. market, but Android fragmentation left Apple as the top overall hardware vendor Android’s multiple vendors are keeping it on top in the U.S. smartphone operating system market, although Apple is still dominant as an individual manufacturer.According to figures released by Nielsen Thursday, Android is the operating system used by 39 percent of smartphones in the United States, followed by Apple’s iOS at 28 percent and RIM’s BlackBerry OS at 20 percent. But because the Android market share is carved up among multiple vendors, Apple’s 28 percent market share makes it the top overall smartphone manufacturer.ANALYSIS: Apple could be the next to ride on the Android gravy train HTC, which is known for popular Android-based devices such as the Evo 4G and the HTC Thunderbolt, is the top manufacturer of Android phones in the U.S., accounting for roughly 36 percent of all Android devices. Motorola, with a 28 percent share of the U.S. Android market, and Samsung, with a 20.5 percent share, round out the top three.There is a big drop-off in market share after Android, iOS and BlackBerry OS. Windows Mobile and Windows Phone 7 devices account for just 9 percent of smartphones in the U.S., followed by HP’s webOS at 2 percent and Nokia’s now-defunct Symbian operation system at 2 percent.Android has continued to expand on the gains that Nielsen reported earlier in the year. According to data released in January, the iPhone OS had captured 28.6 percent of the U.S. smartphone market share, followed closely by BlackBerry OS (26.1 percent) and Android (25.8 percent). Android had accounted for a mere 15 percent of U.S. smartphones in June 2010 before seeing its market share nearly double over the span of five months. Much of Android’s gains have come at the expense of BlackBerry, which has seen its market share in the U.S. decline even as Apple’s has remained steady. Read more about anti-malware in Network World’s Anti-malware section. Technology Industry