He is the subject of a profile in Illustration Magazine issue 47, and his Wikipedia entry is here.
Leafing through the magazine, I soon realized that there was more to Gibson than just those Girls. The man was a master of capturing expressions on a large variety of faces. Plus he was a highly skilled pen-and-ink artist.
Some of this can be seen in the image above from Heritage Auctions. It's from the About Paris illustrations from about 1905. Note how he was able to fade the background subjects using careful linework and perhaps slightly watered-down ink.