Robert Wesley Wilson, also known as Wes Wilson, was a pioneer for psychedelic posters.

Grateful Dead poster by Wes Wilson. (1966)
He is credited for launching the psychedelic art movement as well as for popularizing the psychedelic font, which emulated the trippy LSD experience with its shape which made it look like it was moving.

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I like how the font on this poster looks like flames, although it is a little hard to read, haha
His work is associated with the 1960’s, a time that was defined by the peace movement and psychedelic era. Although he essentially created the style, there were many people who imitated his work and he became easily replaceable. Apparently, his posters were so coveted that they would be stolen not long after they were put up.

(1966)
We can see elements of the Art Nouveau movement in his work. Wilson’s bold use of colour comes from his experience with LSD.

He recently passed away in January, but his legacy will be immortalized- his works have been put up in museums like the New York’s Metropolitan Museum of Art and Museum of Modern Art.

Sources:
www.datebook.sfchronicle.com/art-exhibits/wes-wilson-creator-of-psychedelic-rock-posters-dies-at-82
www.wes-wilson.com/the-psychedelic-poster-art-of-wes-wilson-by-colin-brignall.html