(taken from wikipedia and rewritten just an itty bit)
When Coco Chanel designed her little black dress in the 1920s, Vogue predicted it would "become a sort of uniform for all women of taste". It was simple and accessible for women of all social classes then, and today, is considered an essential element to any woman's warderobe, being extremely versatile in the way it can be dressed up or down depending on the occasion.
The little black dress made its first scandalous appearance in John Singer Sargent's painting "Madame X" at the Paris Salon in 1884, where viewers were so shocked, the artwork had to be removed!
Prior to the 1920s, black was reserved for mourning, and considered indecent if worn in any other circumstances. In 1926, Chanel published a picture of a short, simple, black dress in Vogue magazine. It was calf-length, straight and decorated only by a few diagonal lines.
Because of its economy and elegance, the little black dress was popular throughout the Depression era, albeit with a somewhat lengthened line. During WWII and the ensuing rationing of textiles, the style developed into a commen uniform for civilian women entering the workforce.
The rise of Christian Dior's "New Look" in the post-war era, and the sexual repression of the 1950s, returned the little black dress to its roots as a uniform, as well as turned it into a symbol of the "dangerous" woman. Hollywood femme fatales and fallen women characters slunk around in black halter-style dresses, while housewives and more wholesome film stars were more conservatively attired.
In the 40s and 50s, synthetic fibers became popular, and the increased availability and affordability of many designs were the joy of dressmakers and ordinary women alike.
The generation gap of the 1960s created a dichotomy in the design of the little black dress. The younger "mod" generation preferred a little black minidress, and designers catering to their culture shortened the skirt even more, even creating cutouts or slits, and using sheer fabrics.
Other women aspired to simple black sheath dresses similar to that designed by Hubert de Givenchy for Audrey Hepbrun in "Breakfast at Tiffany's".
In the 1970s, colors won out over black, especially among the disco or jet set. The little black dress became either lacy and feminine, simple and normal (Bill Blass) or skimpy, such as Qiana's one-shoulder form-fitting black dress.
The popularity of casual fabrics for dress and business wearing during the 1980s brought the little black dress back into vogue. The new designs incorporated details already fashionable at the time, such as broad shoulders and peplums.
The grunge culture of the 1990s saw the combination of the little black dress with sandals or combat boots, the dress itself remaining simple in cut and fabric. Since the late 90s and into the 21st century, we have never seen so many creative variations of the LBD!