Most historians trace the origins of the thigh-showing, sexual-revolution-jumpstarting clothing item to the British fashion designer Mary Quant, who took the name for her creation from the Mini autos that were then to be seen all over the Continent. Quant ran a popular shop in the Chelsea section of London which highlighted her own designs; the store was considered influential in what was then developing into the fashion revolution sweeping London and, thenceforth, the world. London was just beginning to swing in the mid-60's as its leading citizens' music and graphical sensibilities were being sent all over the world like spies, infiltrating the brains of young people all over the civilized world. Quant was considered one of the most 'with-it' personalities of the time, and her work was generally studied as a signpost of what sorts of trends were in the ascendant.
Other scholars point to André Courrèges, a French designer who was also coming up with similar ideas at around the same time; he was the person largely credited for creating the Mod look during the spring and summer of 1965. But while Quant's work was created specifically for people to purchase and wear and enjoy, Courrèges was a high-fashion designer who worked in the rarefied world of haute couture - that is, clothes not necessarily meant to be actually worn on the street, but which are modeled at ritzy Paris events to show off what the designer is capable of. One needs to remember that at this time, London was certainly not considered the fashion Mecca they are today; quite the contrary, they were often portrayed as still recovering from the downtrodden postwar period. A young lady in south-west London was all very good and well, but it took a Frenchman with snooty credentials to get the look accepted by the elite.
Then again, Anne Francis was seen to be wearing a mini in the 1956 sci-fi film Forbidden Planet. Ms. Francis's skimpy clothes were considered shockingly (or pleasantly, depending on the sex of the observer) non-existent for the period; but, then, the film's plot was supposed to have taken place in the early 23rd century, by which time we should be over such silly hangups. The costumes on that film were created by Helen Rose, who also designed Grace Kelly's wedding gown when she got hitched to the Prince of Monaco the same year this film appeared. Ms. Rose usually doesn't get credited with the creation of the mini skirt, however.
The skirts started to gain acceptance fairly quickly, owing to the fact that they showed off some of the more delightful portions of young female anatomy. Of course, it took some prodding, as Britain was still a rather conservative place at the time: the nation was going through the same sorts of social changes as the United States.
Jean Shrimpton, one of the most celebrated fashion models of the era, wore a mini skirt to Derby Day (day one of the Melbourne Cup Carnival in Australia), which started tongues wagging. Cathy McGowan, host of the British music show Ready Steady Go, also adopted the look fairly quickly; that program was watched by millions of young English kids every week, and its impact was enormous. Diana Rigg, in addition to her leather catsuits, was wearing mini skirts during the most popular era of the smash TV show The Avengers as well.
The final straw of acceptability might have been when Jackie Kennedy wore a white miniskirt at her wedding to Aristotle Onassis; after all, if it was good enough for a First Lady, it was good enough for anyone, right? The American versions of the mini tended to have hem lines a bit closer to the knee, of course; the British generally ended about 6 or 7 inches above the knee. (Of course, in a country started by Puritans, it's a wonder we got mini skirts at all.)
The mini skirt evolved, or devolved, as time went on. Starting in the following decade, skirts began getting longer again. The mini - once seen as a sort-of symbol of Women's Liberation, a highly visible fuck-you to Talibanesque ideas about how women should clothe themselves - was now being considered just the opposite. Women now wanted to be seen as more than sex objects, and so such styles as the maxi skirt or the granny look became fashionable for a short while.
But, the quest to show more luscious female skin continues unabated, thank Allah. The mini skirt gave way to the microskirt, and to the rah-rah, and to minidresses, and hot pants, etc., etc. What once was concealed, is now more often revealed.
But there's still something irreproducably enticing about seeing those young 60's chicks in photographs from the period, in their milieu, strutting down a city street wearing their minis, looking damn good and knowing it. Maybe it's nostalgia, or maybe everything from the 60's just looks better. Certainly we live in thong-thronged times, when one can see plenty of girly skin in public on any given day; but there remains an allure attached to that look, that era, that... feeling that cannot be duplicated.