The Parrish Art Museum, a distinguished Hamptons home of American art, had many reasons to celebrate on Saturday night at its Midsummer Party. More than 600 guests came to admire and fete the museum in the first summer in its new 34,400-square-foot Herzog & de Meuron-designed building. More than 40 artists were there, including Chuck Close, Ross Bleckner and Bryan Hunt, many of whom advised on the design of the large loft-like galleries. While previous parties for the Parrish Art Museum in its former home had been held in an air-conditioned tent, on Saturday, guests dined in the open air on long tables. Attendees and organizers — who helped raise $1 million for the museum, which celebrates the artistic legacy of Long Island’s East End — included Terrie Sultan, Debbie Bancroft, Beth Rudin DeWoody, Dorothy Lichtenstein, Tony Ingrao and Randy Kempner, Nicole Miller, Jimmy L. Nederlander, his wife, Margo, and father James M. Nederlander. Also there was Stefano Tonchi, Toni Ross (of Nick and Toni’s), Rick and Kathy Hilton, Laurie Waters, Patricia Duff, Jay Snyder and Sharon Bush. While a few party crashers were artfully dealt with, dancing went on late, and a select few slipped out for an after-party at the Hilton’s Southampton home.