Fiorucci - New York City, early 1980s
If you've never heard of it before, Fiorucci (or Fiorucci's as we used to call it) was pretty much the standard for the hip and cool of 1970s New York (think influence on the level of Kitson but much, much more cutting edge). For a while, these little angels where everywhere in the city (including on a Fiorucci sweatshirt I had in junior high), but somehow at some point in the 80s, they flew out of Manhattan with not half the fanfare with which they had arrived.
Joan Didion called the day of the Manson murders, August 9, 1969, the day the 60s ended. If I had to say when the 70s officially ended in New York, I might pick the day Fiorucci left town (even though that didn't happen until some time in the early 80s).