Question: What was the unofficial name of the event that caused the man who defeated the great John L. Sullivan to rescind his retirement after hearing of the outcome?
Sentence (from "Fitzsimmons-Maher Prizefight"): The Fitzsimmons-Maher Prizefight (February 21, 1896), also considered, unofficially, as the 1896 World Heavyweight Championship, occurred between Bob Fitzsimmons and Peter Maher on a sandbar in the Rio Grande River just far enough outside of the American city of Langtry, Texas, in which state boxing was illegal, to be considered technically in the Mexican state of Coahuila de Zaragoza.
Relevant evidence: Yes