"Before the War on Drugs, nobody used those drugs."
Before LSD was made illegal in October 1967, you could go to parties where there were tubs of Kool-Aid spiked with LSD. Some bands would pass out free LSD on strips of paper or even on popcorn. It was readily available either for free or for a dollar or two at most big outdoor concerts.
5000 free doses of STP or DOM (same chemical) was passed out in tabs during The Human Be-In Jan 14, 1967. DOM/STP is illegal now and is just not available unless you know a small-scale clan lab. The same is true for most other substituted phenylethylamines- they are not for sale, except for MDMA, MDEA, and (overseas) methylone. 2-CT-2 and 2-CT-7 were made illegal a little while ago, and I don't run into folks who even know what they are any more.
MDMA used to be legal; it was made illegal in 1985. Prior to that date you could buy it over the counter in some bars, I remember some in Texas where that was common, and a few other places in NY and CA. It was much more common then to see someone under the influence, people spoke of it, it was legal, heck, and was basically all over the place. It became pretty popular starting in, I think, 1972 along with its cousin MDA.
Foxy Methoxy (5-Methoxy Diisopropyltryptamine, 5-MEO DIPT) was made illegal in April 2003. Prior to then you could go online and buy gram quantities with a credit card from places like Duncanlabs, omegafinechemicals, pondman.nu, RACResearch and a bunch of others. These guys sold lots and lots of it and other tryptamines, it was common in the club scene and on campuses. It's illegal now.
Each one of these chemicals were made scarce and expensive by making them illegal. There has been no big explosion of Foxy use since 2003, and there is not lots of LSD around, although there is some. There is a fair amount of MDMA available, though, but from what I can see nothing like when it was legal.
True absinthe, containing thujone, has not been available (unless you make it yourself or smuggle it in) since just past the War of Northern Agression. While it is still avalable overseas, it is just not popular in the USA- no explosion of abuse since it was made illegal over a hundred years ago.
LSD was invented in 1938, and Hoffman "discovered" it in 1943. Most of the amphetamines were discovered also in the late '30s. Sasha Shulgin did synthesize lots of stuff in the 70-80 period, but his favorite, MDMA, was invented in Germany in 1937 or so. Heroin was cooked up in the late 1800's, and marijuana has been around for as long as there have been plants.
The fentanyls were indeed invented during the WOsD, but for medical use, not dreamed up as a recreatinal compound like foxy or E. Some fentanyl hybrids like China White show up every now and then, but it's cheaper to make heroin than it is to synthesize fentanyl, especially at home on a stove.
Minor clarification- Posession of LSD was illegal in Oct 1967, but it was not made a Schedule 1 drug until October 27, 1970, along with all of the hallucinogens they could think of (like DMT, STP, psilocybin).
Personally I think that researchers should be able to use these drugs for therapy and other uses. Once a body of literature is built up based on honest research, it will be clearer to see which of the tens of thousands of psychoactive compounds are useful, harmless, or irrelevant.