It's official: Seattle's best clothier is finally opening a big store in the Big Apple. Nordstrom confirmed that it will open a long-awaited Manhattan flagship at Broadway and West 57th Street. The Post first reported the location Tuesday on its website. At a splashy SoHo press conference yesterday with Mayor Bloomberg at his side, Pete Nordstrom, president of merchandising for the luxe retailer, said the 285,000-square-foot store will stretch seven stories high — two more than the next-tallest shop in the 231-store chain. "We fully expect this to be our most productive store," Nordstrom said. Officials said it will be located at 225 W. 57th St., anchoring a mixed-use skyscraper that will be erected by New York real-estate mogul Gary Barnett of Extell Development. Bloomberg called the new Midtown tower, which is slated to open in 2018, "a smart fashion statement," gushing that it will create 1,000 new jobs and 5,000 construction jobs.