Some of the most important fashion designers began as milliners. Coco Chanel in 1910. Charles James in 1925. And Roy Halston Frowick in 1953. Frowick shortened his name to “Halston” in 1957, when he opened his first hat shop, and he achieved his first fame in 1961, when he designed the pillbox hat that Jackie Kennedy wore to her husband’s inauguration as president. It’s a pillbox on steriods. Creating for the head, which is round, teaches designers about shape—how to work with curves and volume. Halston would go on to design for the body, making sinuous dresses and ensembles that can appear under-constructed. Don’t be fooled. His clothes are brilliantly cut. This exhibition, highlighting the hats and hair accessories that Halston made for the luxury store Bergdorf Goodman, is a view to Halston’s formative phase. —L.J.