At the time the film takes place, no building in Los Angeles was allowed to be taller than City Hall, so the cameras were placed at certain points so that any building taller than City Hall would not be seen.
When promoting his program "The Loudest Voice" on the Howard Stern show, Russell Crowe said this was one of two films where he wishes there was a sequel as he liked playing the character. The other film is Les Bons Gars (2016).
According to Guy Pearce on the DVD commentary, he attended a James Ellroy one-man show in his native Melbourne, Australia, while the film was in pre-production. Pearce notes that during a Q&A session following Ellroy's performance, an audience member asked if any of Ellroy's books would ever be adapted into film. Ellroy replied that not only was L.A. Confidential in pre-production, but two Australian natives (Pearce and Russell Crowe) were cast in the film. The audience erupted into laughter, thinking that Ellroy was playing a wry joke on the audience by randomly naming two local actors and claiming they were cast in a big-budget Hollywood film. Pearce, who was sitting in the audience, was mortified. It was only a year later that the audience learned that Ellroy was, in fact, telling the truth.
James Ellroy describes the character of Bud White as the biggest cop on the Los Angeles force. Noting that he wasn't even six foot, Russell Crowe decided to move into an apartment so small that he had to duck to get into the doorways, and could barely stand up. Crowe said this worked in making him feel like a "giant" by the time he came to the set to shoot.
James Ellroy described Kevin Spacey's performance of Jack Vincennes as "Some of the best self-loathing I've ever seen on-screen."