The smartphone boom seems to have no end in sight, and for the moment, HTC is right at the forefront. Though Samsung is selling the most units worldwide, HTC has cornered the lucrative American market: according to Business Week, the Taiwanese manufacturer finished out the third quarter with 24 percent market share in the United States. That narrowly beats out Samsung with 21 percent, and Apple with 20 percent.

Not all of those impressive sales are Android, of course; HTC is one of the most popular sellers of Windows Phone 7 devices, and I’m sure there are still a few Windows Mobile holdouts. But with Android sitting pretty at more than 40% of the smartphone market, and Windows Mobile and Windows Phone 7 together claiming about 10%, it’s fair to say that HTC’s fortunes are currently resting on little green robots. Major upcoming phones for HTC include the Rezound on Verizon, expected at the company’s New York City announcement tomorrow, and the Vivid (codename Holiday) on AT&T, one of the first phones to take advantage of the carrier’s new 4G LTE network.

HTC’s bottom line is healthy, as well. The company announced that it had shipped 13.2 million devices worldwide in the third quarter, for an equivalent of $4.54 billion in total revenue, with an impressive 13.76% profit margin. That’s a 93% increase year-over-year. Unfortunately HTC’s outlook for Q4 isn’t nearly as rosy; the company expects sales to be essentially flat. With the iPhone 4S and new Samsung phones on all U.S. networks, it’ll be a photo finish to see who ends the fiscal year in first place.

[via SlashGear]