Harley culture has an interesting history going back to the 1920's or so in this country. But the more interesting bit ... and the bit that still influences "the look" of today's group of HD Weekend Pirates, really started in earnest after WW2 with returning Vets looking for some thrills.
Someone mentioned the Hollister, California event (inspiration for Brando's
The Wild One.) In typical Hollywood style, the event was overblown in the film but still fun to watch even today. Brando's "Johnny" is emblematic of the One Percenter, his character was copied buy dozens of tacky biker movies throughout the 1960's.
But there were real riding groups (Gangs?) and they were there well before the films. Where do you think Hollywood got the idea? From real biker gangs.
I grew up in L.A. and saw my fair share of REAL Hell's Angels, Statin Slaves and Mongols. Up close and personal. This was in early 60's but the gangs were around before that. But by the 60's they got really strong and organized ... all the while HD was paying attention, but the company was on the rocks, barely surviving at that point. Remember, the Hard Core bikers were the ONLY ones to stand by HD when it was near total failure, then during the dark AMF buy out ... everyone else, old and young wrote HD off. The old folks switched to Honda Gold Wings, young riders went dirt riding or sport riding ... and NO ONE but BIKERS bought HD.
Question for HD was ... do we disown these hoodlums? Or embrace them? HD embraced them ... but at a safe distance and it came later, in the 1980's.
What I find interesting is how Harley-Davidson walked the thin, sharp edge, using the "Bad Ass Biker" image to sell thousands of bikes and hundreds of millions of dollars in riding gear, yet carefully dodged direct connection with actual Biker Gangs. Public relations genius, IMO.
By the 80's the community began to shift in a major way. Old guys were dying off, Baby Boomers were coming in. After the Evo motor came along in 1985, things really changed. Harley's got reliable and the Lawyers, Dentists and Real Estate developers began their Mid-Life Crisis rides. This still goes on today.
This group of RUBS (Rich Urban Bikers) grew the brand to huge proportions and made riding a Harley an acceptable activity. (It's OK dear, they just look like Pirates, they're not real! ...

)
One of the more interesting manifestations is how HD culture has expressed itself in countries outside the USA. Like serious bad ass bike gangs in Norway and Sweden ... WTF!!!
Our riding group used to travel to Death Valley twice a year. Did this for 15 years. Nearly every time we go we run into Foreign Riders on (mostly) rented Harley's. Most organized tours.
I've met BIG French and German groups, 20 to 25 riders in each group. They have a ball, all dressed in the nicest HD leather outfits you could imagine ... and ALL ready to party! The Typical Euro tour would be: Fly into Vegas, ride out to Grand Canyon then Death Valley and back to Las Vegas to fly home. Usually 3 to 4 day tour.
Some hard core guys ship their own Harleys over. BIG MONEY. We have even seen a group of Japanese on rented Harley's. (about 8 riders). Also have run into groups from: Brazil, Argentina, Spain, Norway, Denmark, Sweden. Simply amazing. The HD brand does, indeed, have very long legs!
These guys did nothing but buy things. Most organized tours had chase vans (towing spare bike or two) so they could load up on trinkets, just load then into to the 15 passenger vans.
The HD Gang connection is also interesting to me. Books have been written about this ... and some of the HD branding really originates from the gangs. HD try to disavow and distance ... but secretly sit back and chuckle .... and rake in the cash. They've exploited the bad boy image to the max.