Mary Shelley began writing Frankenstein in 1816.
The idea took shape during the unusually cold, rainy summer of 1816, when Shelley was staying near Lake Geneva with Percy Bysshe Shelley, Lord Byron, Claire Clairmont, and John Polidori. Byron suggested that each person write a ghost story. After struggling to invent one, Mary experienced the famous waking vision of a scientist assembling and animating a human body.
She initially imagined a short story, but Percy Shelley encouraged her to expand it into a novel. She wrote the early chapters in 1816 and continued revising and developing the manuscript into 1817. The completed work was published anonymously in London on 1 January 1818 as Frankenstein; or, The Modern Prometheus.
The dates 1816, 1817, and 1818 therefore describe different stages. 1816 marks the beginning of composition; 1817 is the year in which Shelley completed much of the manuscript and prepared it for publication; and 1818 is the publication year. The story’s creation is also linked to the atmospheric effects of Mount Tambora’s 1815 eruption, which contributed to 1816’s nickname, the “Year Without a Summer.”