Pikesville-based America's Realty LLC has purchased its first shopping mall in the largest single-property transaction in the company's history. America's Realty CEO Carl Verstandig said his firm paid $27 million for the Iverson Mall in western Prince George's County, a price that will allow the company to charge $11 per square foot to retailers. That rental rate, which is virtually unheard of in the Washington area, has already attracted a Rose's store to the 800,000-square-foot shopping center…