Another line in the sand crossed at Motorola (NYSE: MOT). Samsung has ousted the American handset maker from its number one position in the US market. Research firm Strategy Analytics reports that the Korean electronics maker edged ahead in the third quarter taking 22.4 percent of the US handset market, compared with Motorola which had a 21.1 percent share. It also reported that the US market grew 6 percent in the third quarter, with 47 million handsets shipped.

The US—the world’s single largest handset market—has been Motorola’s traditional stronghold, where it accounts for half of the company’s total sales of mobile devices, about $1.55 billion in Q3. Strategy Analytics found that Samsung’s ability to deliver an “attractive high-tier handset portfolio” for the big four operators “proved crucial” in helping it take the leading market share in the US. Don’t expect Motorola to take back that title anytime soon. In its Q3 earnings call, the handset maker expects Q4 to be worse in terms of sales, while the first half of 2009 will be hit as the company tries to retrench and shift its mobile handset strategy.

Moreover, its competition is only increasing. Korean rival LG (SEO: 066570) has a 20.5 percent share, giving it the third biggest share of the market. It’s not difficult to see it overtaking Motorola in the coming quarters. Strategy Analytics also found that smartphone maker RIM (NSDQ: RIMM) maintained its double digit growth marketshare for the second straight quarter in Q3, giving it a 10.2 percent of the US market. Apple (NSDQ: AAPL) too is coming up. It has a 5.7 percent share of the market putting it in sixth position. Nokia (NYSE: NOK), meanwhile, which has struggled to gain traction in the US market has an 8.4 percent share of the market, putting it in 5th position.