Written in the summer of 1926, The Call of Cthulhu was first published in the pulp magazine Weird Tales in February 1928. It is the only story written by Lovecraft in which the extraterrestrial entity Cthulhu himself makes a major appearance. The story is written in a documentary style, with three independent narratives linked together by the device of a narrator discovering notes left by a deceased relative.
The first seed of the story's first chapter The Horror in Clay came from one of Lovecraft's own dreams he had in 1919, which he described briefly in two different letters sent to his friend Rheinhart Kleiner on May 21 and December 14, 1920. In the dream, Lovecraft is visiting an antiquity museum in Providence, attempting to convince the aged curator there to buy an odd bas-relief Lovecraft himself had sculpted, who initially scoffs at him for trying to sell something recently made to a museum of antique objects. Lovecraft then remembers himself answering the curator with the response
"Why do you say that this thing is new? The dreams of men are older than brooding Egypt or the contemplative Sphinx, or garden-girdled Babylon, and this was fashioned in my dreams."
This can be compared to what the character of Henry Anthony Wilcox tells the main character's uncle while showing him his sculpted bas-relief for help in reading hieroglyphs on it which came through Wilcox's own fantastical dreams:
"It is new, indeed, for I made it last night in a dream of strange cities; and dreams are older than brooding Tyre or the contemplative Sphinx, or garden-girdled Babylon."
Lovecraft then used this for a brief synopsis of a new story outlined in his own Commonplace Book at first in August 1925, which developed organically out of the idea of what the bas-relief in the dream actually might have depicted. In a footnote for his writing down of his own dream, Lovecraft then finished with the suggestion "Add good development & describe nature of bas-relief" to himself for future reference.
FLEUR-DE-LYS STUDIO
DATE(S) VISITED: OCT 29, 2016
LOCATION: PROVIDENCE, RI
His card bore the name of Henry Anthony Wilcox, and my uncle had recognized him as the youngest son of an excellent family slightly known to him, who had latterly been studying sculpture at the Rhode Island School of Design and living alone at the Fleur-de-Lys Building near that institution. - HPL ~ The Call of Cthulhu
WILLIAMS STREET
DATE(S) VISITED: OCT 29, 2016
LOCATION: PROVIDENCE, RI
The professor had been stricken whilst returning from the Newport boat; falling suddenly, as witnesses said, after having been jostled by a nautical-looking negro who had come from one of the queer dark courts on the precipitous hillside which formed a short cut from the waterfront to the deceased‘s home in Williams Street. Physicians were unable to find any visible disorder, but concluded after perplexed debate that some obscure lesion of the heart, induced by the brisk ascent of so steep a hill by so elderly a man, was responsible for the end. At the time I saw no reason to dissent from this dictum, but latterly I am inclined to wonder—and more than wonder. - HPL ~ The Call of Cthulhu
WATERMAN STREET
DATE(S) VISITED: OCT 28, 2016
LOCATION: PROVIDENCE, RI
On March 23d, the manuscript continued, Wilcox failed to appear; and inquiries at his quarters revealed that he had been stricken with an obscure sort of fever and taken to the home of his family in Waterman Street. He had cried out in the night, arousing several other artists in the building, and had manifested since then only alternations of unconsciousness and delirium. - HPL ~ The Call of Cthulhu