Douglas Harper's Etymology Dictionary
Gibson girl
"woman considered stylish late 1890s and early 1900s," 1901, named for U.S. artist and illustrator Charles Dana Gibson (1867-1944), whose main model was his wife, Irene Langhorne (1873-1956). The Gibson cocktail (attested by 1914) is in some stories ascribed to him, but the origin of that term is unknown.
Wikipedia
Gibson Girl
The Gibson Girl began appearing in the 1890s and was the personification of the feminine ideal of physical attractiveness portrayed by the satirical pen-and-ink illustrations of illustrator Charles Dana Gibson during a 20-year period that spanned the late 19th and early 20th century in the United States and Canada. The artist saw his creation as representing the composite of "thousands of American girls."