Facebook's user base is nearly as large as the U.S. population and, for the first time, the site has turned a profit.

That was the double-barreled announcement Tuesday from Facebook CEO Mark Zuckerberg, who thanked the site's users for helping its online community cross the 300 million threshold. There are about 307 million people living in the United States, according to the U.S. Census Bureau. Read More "We're just getting started on our goal of connecting everyone," Zuckerberg wrote on the company's blog.

"Because we want to make it as easy and fast as possible for the world to connect, one of the things we think a lot about is how to make Facebook perform even faster and more efficiently as we grow," he wrote. "We face a lot of fun and important challenges that require rethinking the current systems for enabling information flow across the Web."

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