Pecos Bill is a cowboy, apocryphally immortalized in American folklore set in the Old West during American westward expansion into the Southwest of Texas, New Mexico, Southern California, and Arizona. Their stories were probably invented as short stories and a book by Edward S. O'Reilly in the early 20th Century and are considered to be an example of fakelore. Pecos Bill was a late addition to the "big man" idea of characters, such as Paul Bunyan or John Henry.
The first stories were published in 1917 by Edward O'Reilly for The Century Magazine, and collected and reprinted in 1923 in the book Saga of Pecos Bill (1923). O'Reilly said they were part of an oral tradition of tales told by cowboys during the westward expansion and settlement of the southwest including Texas, New Mexico and Arizona. But American folklorist Richard M. Dorson found that O'Reilly invented the stories as "folklore", and that later writers either borrowed tales from O'Reilly or added further adventures of their own invention to the cycle. One of the best-known versions of the Pecos Bill stories is by James Cloyd Bowman in Pecos Bill: The Greatest Cowboy of All Time (1937), which won the Newbery Honor in 1938 and was republished in 2007.
Edward "Tex" O'Reilly co-authored a cartoon strip with cartoonist Jack A. Warren, also known as Alonzo Vincent Warren, between 1929 and 1938. When O'Reilly died in 1938, Warren began a strip titled Pecos Pete. This was a story about "Pecos Bill", who had received a "lump on the naggan" that caused him amnesia. The cartoons originally were published in The Sun and were later syndicated. He also has a wife, named Slue-Foot Sue.