The 1970s late 1970s
Studio 54 and Disco Culture
The club that opened in April 1977 didn't invent disco fashion, but it concentrated it into a single, photographed, endlessly imitated dress code that reached far past Manhattan.
Studio 54 opened at 254 West 54th Street in April 1977, and I think what actually made it a fashion event rather than just a very famous nightclub is how deliberately visual the whole operation was - Steve Rubell and Ian Schrager ran door policy like casting a room, mixing genuine celebrities with dancers, models, and whoever looked interesting that night, under a lighting rig and mirrored sets built specifically to be photographed. That combination - a curated crowd, dramatic lighting, and a constant photographer presence - is exactly why what people wore there became fashion news instead of staying a private nightlife story.
The actual clothes are worth being specific about. Bianca Jagger's white Halston suit and her infamous entrance on a white horse for her birthday in 1977 is probably the single most reproduced image of the era's eveningwear; Liza Minnelli, part of Halston's inner circle off the runway as much as on it, was photographed there constantly in his slinky bias-cut jersey. Halston himself was a regular, which mattered commercially - a designer's actual social circle wearing his clothes in the same rooms being photographed by the same press was a kind of marketing no ad campaign could fully replicate. The look that trickled down from all of it was fairly consistent: body-skimming jersey or lurex and metallic fabric, halter necklines, minimal underpinning, cut to move under strobe lights and catch whatever shine was available on the dance floor - the full package covered in the disco silhouette entry.
What I think is genuinely interesting is how fast and how far that trickled down past the velvet rope. Roller discos, department-store "disco departments," and pattern companies selling home-sewable halter-dress patterns all show up by 1978-79, meaning a look built for one specific, exclusive Manhattan room got translated into something a teenager in a mall could plausibly assemble within about two years. Studio 54 itself closed under legal trouble in early 1980, barely outlasting the decade it's now shorthand for - but the dress code it crystallized had already fully escaped the building well before that.