“The opera is where society puts itself on display,” says Carrie Coon’s character Bertha Russell in “The Gilded Age.” She is correct, but in HBO’s period drama set in late 19th century New York City, society is always on display and nearly every scene is a showcase for the luxe sartorial indulgences of the elite.

Created by “Downton Abbey” mastermind Julian Fellowes, “The Gilded Age” is a soapy saga in which old money begrudgingly rubs elbows with the nouveau riche. The 1880s were a period of rapid industrialization, political corruption and an ever-widening gap between the wealthy and the poor. And from the series’ very first episode, costume designer Kasia Walicka-Maimone wanted to capture the spirit of excitement that defined the era. “There were those giant socio-economic differences that were visible daily on the street,” she said. “The ladies of means, the ladies who had money, it was their town,...