Takes place on sets from Gunsmoke, specifically a re-dressed Long Branch Saloon.
Actors in this episode bringing actual boxing experience to the screen: Richard Boone boxed during his time in the U.S. Navy, Don Megowan boxed while in the U.S. Army, Hal Baylor was an amateur and professional boxer, with Jack Perry having been a professional boxer in the lightweight class in the 1910s-1920s.
Paladin (Richard Boone) and Joe Roland (George E. Stone) have a briefly alluded to backstory in Philadelphia. In the era of this series (1870s), San Francisco had a population over 150,000 (10th largest in the USA) and Philadelphia was the second largest city in America with more than 675,000 residents.