50 Years (1969):
* Foundation of Panther in the UK and Ballantine in the USA, both publishers who did sterling work to bring H.P. Lovecraft, R.E. Howard, and the writers of the Lovecraft Circle, to the masses.
* Arkham publishes its two-volume Tales of the Cthulhu Mythos, the first multi-author Mythos anthology book.
* French literary journal Le Cahier de l’Herne famously devotes its entire issue to Lovecraft.
80 Years (1939):
* Arkham House founded in 1939, and the first title published — The Outsider and Others.
100 years (1919):
* Lovecraft publishes the story “Dagon”.
(My thanks for Martin A. for correcting my ‘slip of the memory’ on “Dagon”. When first published the above post said the story was written in 1919. The story was, of course, published in 1919).