Handset maker Samsung was once again the top mobile phone manufacturer in the United States in the first quarter of 2012, according to the market researchers at comScore. But the platform behind most of Samsung's devices, Google Android, saw even bigger gains: It now accounts for 50 percent of all smartphones used in this country.

"Google Android continued to grow its share in the US smartphone market, crossing the 50-percent threshold in February to capture a majority share for the first time in its history," comScore noted in a press release. "Device manufacturer Samsung ranked as the top mobile devices OEM."

The two scores aren't entirely related. Samsung's win is for "mobile devices" overall and includes "dumb" phones as well as smartphones and other devices. In this category, Samsung retained the same 25.6 percent usage share it saw in the previous quarter. Number-two LG fell 5 percentage points to 19.4 percent usage share, and number-three Apple climbed a bit to 13.5 percent market share. There are 234 million mobile devices in use in the United States, comScore says.

The researchers at comScore separately noted that there are now more than 52 million Android handsets in use in the United States, a figure that gives Android just over 50 percent usage share in the smartphone market specifically. Number-two Apple climbed slightly to 30.2 percent usage share, while number-three Research In Motion (RIM) continued its downward spiral, dropping over 3 percentage points to 13.4 percent share. A total of 104 million people use smartphones now in the United States, comScore says. This data suggests that smartphone usage is closing in on 50 percent of the total mobile device market—a milestone it could surpass later this year.

For some reason, comScore doesn't break down the top smartphone hardware makers company by company. Samsung was the number-one maker of mobile devices and smartphones for all of 2011, but Apple experienced a temporary bump at the release of its iPhone 4S to take the top spot in that final quarter of the year. Many analysts expect Samsung to rebound and re-take the top spot in the first quarter of 2012.