Although the series title had a hyphen, Paladin's business card did not.
Parts of the first season episode "The Colonel and the Lady" were filmed on sets used for the television show "Gunsmoke" (1955). The Long Branch Saloon is very minimally redecorated to stand in for a saloon Paladin visits in a Nevada mining town. Shots of people walking the streets of the town were also taken from Gunsmoke.
Filling out Paladin's back story in the early episodes, it is mentioned that he was a West Point graduate and former professional soldier before the Civil War. Paladin never mentions directly which side he was on during the war.
While many television series are taken from radio shows, the radio show “Have Gun Will Travel” with John Dehner as Paladin appeared after the television show.