Diego Valdez is a famous western robber of the Domingo Baca Trail from 1875 to 1880 who came to be known as the nickname El Diablo.
El Diablo's trademark is a black outfit and mask. He fell in love with and married the singer/songwriter Lizzie Applegate. Lizzie built a house for them in which she stashed the Christmas Gold coins (which came to be known as such due to being stolen on Christmas Day, 1878), and set up a series of puzzles for him to solve in order to find it once he returned from his quests. Unforunately, he never did.
Diego maintained in his letters to Elizabeth that he was a good man, stealing money for the right reasons and to give it to the poor. He married Elizabeth on June 18, 1876.