The Wineville Chicken Coop Murders were a real series of child abductions and murders that took place in California in the mid-1920, ending in 1928 when Gordon Stewart Northcott was arrested and convicted of the murders of over twenty children. The case was also the basis of the 2008 Clint Eastwood film, Changeling (2008).
When John (Wes Bentley) looks into the guest book, the last entry states "I am the zodiac" with the symbol from the famous zodiac murders.
John Wayne Gacy, aka "the Killer Clown", is portrayed by John Carroll Lynch. Lynch had previously appeared in American Horror Story: Freak Show as Twisty the Clown, another killer clown that is said to have been inspired by Gacy.
The character of Aileen Wuornos (Lily Rabe) is introduced with the song "Carnival" by Natalie Merchant. In real life, Wuornos loved the song and requested it for her funeral after her execution in 2002; the song was also used in the end credits of the 2003 Wuornos documentary Aileen: Life and Death of a Serial Killer (2003).