Originally, part 3 was intended to be a prequel, telling the story of the very first Purge. This idea was scrapped when Frank Grillo accepted James DeMonaco's offer to reprise the character of Sergeant Leo Barnes. The prequel idea was used for the next film in the series, The First Purge (2018).
As of this film, each Purge installment has earned more money at the box office than its predecessor. A rare feat for horror/thriller series.
Edwin Hodge's character is in all three of the Purge movies. In the first two, he was credited as Bloody Stranger. In this one, his name is revealed to be Dante Bishop.
The Purge has expanded its universe more throughout each film. The first film takes place in a house. The second film takes place in the streets. The third film takes place in the government. Also, each film looks at the Purge through different points of view. The first film is told from the rich. The second is told from the poor. The third is told from the political side.