NEW YORK — After all the hype, Facebook’s first day as a public company ended where it began. Its stock closed at $38.23, up 23 cents, after pricing Thursday night at $38 per share. After an anxiety-filled half-hour delay, Facebook stock began trading on the Nasdaq Stock Market for the first time as investors were finally able to put a dollar value on the company that turned online social networking into a global cultural phenomenon. The stock opened at 11:32 a.m. at $42.05, but soon dipped to $38.01. By noon, it was up again at $40.40, a 6 percent increase. It fluttered throughout the afternoon, but it never hit the double-digit jump that many Facebook-watchers had expected. By the end of the day, more than 500 million shares had changed hands. The closing price means Facebook is worth about $105 billion, more than Amazon.com, McDonalds and storied Silicon Valley icons Hewlett-Packard and Cisco. But as many people looked for a big first-day pop in Facebook’s share price, the single-digit increase was somewhat of a letdown. “It wasn’t quite as exciting as it could have been,” said Nick Einhorn, an analyst with IPO advisory firm Renaissance Capital. “But I don’t think we should view it as a failure.” Indeed, the small jump in price could be seen as an indication that Facebook and the investment banks that arranged the initial public offering priced the stock in an appropriate range. It’s also a supply-and-demand issue. Facebook offered nearly 20 percent of its available stock in the IPO, so there was enough to meet demand. In comparison, Google offered just 7.2 percent of its stock when it went public in 2004 — and rose 18 percent on day one. Earlier Friday, the company’s 28-year-old CEO, Mark Zuckerberg, smiled as he rang the opening bell from Facebook’s headquarters in Menlo Park, Calif. Surrounded by cheering Facebook employees and wearing his signature hoodie, he pushed the button that signals the opening of the stock market in New York. “Right now this all seems like a big deal. Going public is an important milestone in our history. But here’s the thing, our mission isn’t to be a public company. Our mission is to make the world more open and connected,” Zuckerberg said. Afterward, employees tried to get back to business as usual, building the company under immense new pressure to meet shareholders’ expectations. On Thursday, Facebook and the investment bankers settled on a price of $38 per share. The company and its early investors raised $16 billion in the offering, which valued Facebook at $104 billion. That makes Facebook the most valuable U.S. company to ever go public. Now, the stock market will begin assigning a dollar value to Facebook that will rise and fall with investor whims. It will be subject to broad economic forces and held accountable for profit it earns –or loses– from one quarter to the next. But Facebook is a rare company whose IPO transcends Wall Street’s money lust. It is a cultural touchstone for the way technology reshapes our lives. Since its start as a scrappy network for college students, Facebook has come to define social networking by getting people around the world to share everything from photos of their pets to their deepest thoughts. It has done so while becoming one of the few profitable Internet companies to go public recently. It had net income of $205 million in the first three months of 2012, on revenue of $1.06 billion. In all of 2011, it earned $1 billion, up from $606 million a year earlier. That’s a far cry from 2007, when it posted a net loss of $138 million and revenue of $153 million. The company makes most of its money from advertising. It also takes a cut from the money people spend on virtual items in Facebook games such as “FarmVille.” Facebook’s public debut marks a new milestone in the history of the Internet. In 1995, Netscape Communications’ IPO gave people their first chance to invest in a company whose graphical Web browser made the Internet more engaging and easier to navigate. Its hotly anticipated IPO lit the fuse that ignited the dot-com boom. That explosion of entrepreneurial activity and investment culminated five years later in a devastating bust that obliterated the notion that the Internet had hatched a “new economy.” It took Google’s IPO in 2004 to prove that an Internet company with a disruptive idea could be profitable. In the process, the Internet search leader is forcing other industries to adapt to a new order in which people have come to expect to be able to find just about anything they want by entering a few words into a box on any device with an Internet connection. Facebook’s IPO heralds a new phase of the Internet’s evolution. This social era makes connections among people as important as Google’s massive index of Web links. Still, the IPO will raise new pressures for Facebook to generate more revenue, perhaps by digging further into the trove of revealing information that people share on the network to sell even more targeted ads.