When the bartender asks Harper if he wants a "coonass" beer, he means a Cajun (or local) beer.
During post-production, director Stuart Rosenberg hired composer Charles Fox to do additional scoring, integrating the composer's melody "Killing Me Softly With His Song", into the movie. The song had been a #1 hit two years prior, while Fox was scoring Rosenberg's previous film, The Laughing Policeman (1973).
Paul Newman once said of the Lew Harper character in the "Paul Newman: A Life" (2009) biography by Shawn Levy: "I simply adore that character because it will accommodate any kind of actor's invention . . . It's just lovely to get up in the morning, it's great to go to work because you know you're going to have a lot of fun that day".
This marked a re-teaming of Paul Newman, Joanne Woodward and Anthony Franciosa, all of whom appeared in The Long, Hot Summer (1958).
The studio sound-stage that was used to house "the drowning pool" was Stage 15 at the Warner Brothers Burbank Studios. The stage had been used previously for the marlin fishing scenes in The Old Man and the Sea (1958) and the Arctic ice floe sequence in The Great Race (1965).