According to the report, a big part of Apple's nine point jump can be attributed to sales of the Verizon iPhone in the quarter.
"Apple and Verizon had a very successful launch of the iPhone 4, which allowed the iPhone to expand its market share that was previously held back by its prolonged carrier exclusivity with AT&T," said Ross Rubin, executive director of industry analysis at NPD. "While some of that growth came at the expense of Android operating system (OS), Android models still accounted for half of all smartphones sold in the quarter."
More data from the NPD report.
Sales by mobile OS in Q1 2011:
Android - 50% (down from 53%)
iOS - 28% (up from 19%)
Blackberry - 15% (down from 19%)
Largest handset brands in the U.S.:
Samsung - 23%
LG - 18%
Apple - 14%
HTC, Motorola and RIM followed
Top five mobile phone handsets for the quarter:
Motorola Droid X
HTC EVO 4G
HTC Droid Incredible
For the first time, smartphones accounted for more than half of all mobile phones sold in the US (54%).