BDSM is not anything new: it has been with us ever since the beginning of time.
If you think about it, the first time that a cave man grabbed his old lady by the hair, forcing her to the mats and having sex with her was an early examples of BDSM. The biggest problem with those first sessions, was the fact that there were no safe words.
You can see many aspects of BDSM behavior in the mating habits of most animals species. From a gentle bite on your lover's neck or the properly timed sensual slap on their ass to the playful wrestling match, these are all parts of the BDSM play book. They are shown in the Kama Sutra, ancient Chinese texts and almost every European sex manual. What book of Elizabethan erotic would be complete without a little bit of submission and/or caning?
All those books describing European 'houses of joy' with lingerie-clad serving wenches have their roots in real life. They did and do exist, but they aren't any place where the average Joe could find them There were private clubs for the rich and famous: our Victorian ancestors wrote about them in great detail.
BDSM as we know it today began with the returning GI's of WWII. They returned to the US, and with their new-found freedoms and their GI benefits, they were buying motorcycles, free-range traveling around the US. These GI's were already used to military structure and they found it quite easy to import this structure into the motorcycle clubs. They had seen pain and death, and they were looking for experiences that were 'pushing the envelope'. These GI's had traveled around the world, and now they were incorporating those new feelings into their interpersonal relationships. It became important to be someone who could do, be and expedience more than the next man.
This group of post-WWII began allowing new, younger men into their clubs. The amalgam that was formed during the 50's and 60's became the "Old Guard" that we know today. It should be noted that between old age and AIDS, few of the Old Guard are still alive today.
Starting in the late 50's and early 60's, a new phenomenon began. With the advent of pin-up and detective pulp magazines and the beginning of sexual revolution, heterosexual couples began exploring alternative sexual lifestyles and BDSM.
During the early 70's many magazines like "Latent Image", "Aggressive Gals"; newspapers like "Fetish Times" and "The Berkeley Barb" started running personal ads allowing people to seek out others of like interest. BDSM clubs like TES, BackDrop, Janus, Gemini (and many, many other groups) formed throughout the US.
Once people found alt.sex.bondage on the Internet, they began corresponding directly with other people. They started having munches and play parties, and the rest as they say is history