The El Royale was built from scratch on a sound stage with much of the furniture and decor being custom made (including branded matchboxes and coasters for the bar). The color scheme was meticulously set out so that the California side was mostly yellows and oranges, while the Nevada side was purples and blues. Red was reserved for the borderline, jukebox, and chandelier, while green is almost entirely absent until the end.
The El Royale is based on the famous Cal Neva Resort and Casino that was once owned by Frank Sinatra.
Assuming the Richard Nixon press conference shown on TV is happening live (or earlier that day), the film takes place on Jan. 27, 1969.
Shot on actual film without traditional set-lighting. The hotel was designed to allow enough light to shoot by.