A week ago, reporters and editors in the combined newsroom of DNAinfo and Gothamist, two of New York City’s leading digital purveyors of local news, celebrated victory in their vote to join a union. On Thursday, they lost their jobs, as Joe Ricketts, the billionaire founder of TD Ameritrade who owned the sites, shut them down. At 5 p.m., a post by Mr. Ricketts went up on the sites announcing the decision. He praised them for reporting “tens of thousands of stories that have informed, impacted and inspired millions of people.” But he added, “DNAinfo is, at the end of the day, a business, and businesses need to be economically successful if they are to endure.” All other articles promptly vanished from the sites; an official at DNAinfo said they would be archived online. Mr. Ricketts wrote that he founded DNAinfo in 2009 “because I believe people care deeply about the things that happen where they live and work,” and he thought he could build “a large and loyal audience that advertisers would want to reach.” DNAinfo and Gothamist, which Mr. Ricketts bought in the spring, attracted more than 9 million readers a month, in New York and other cities where they operate satellite sites, DNAinfo said. Read more at The New York Times.