The woman from the dream Jessie describes as standing over a well during an eclipse is Dolores Claiborne, the main character from Stephen King's 1992 novel of the same name.
The book (Midnight Mass) that Jessie throws at the dog in this movie was written by Kate Siegel's character from Hush (2016) which was also directed by Mike Flanagan.
Gerald refers to the dog as Cujo, which is a reference to the Stephen King book by the same name.
When Gerald says, "All things serve the beam," this was a reference to author Stephen King's "Dark Tower" novel series.
In the novel, the solar eclipse in question is the one of July 20, 1963, whose path of totality crossed Maine. In the movie, it is presumably the one of May 30, 1984, whose path of totality crossed New Orleans.
When Jessie talks about the Moonlight Man's Bag of Bones, this is a likely reference to Stephen King's novel of the same name.
Carla Gugino (Jessie Burlingame), Henry Thomas (Tom) & Kate Siegel (Sally) also worked together on The Haunting of Hill House (2018) as Olivia, Young Hugh Crain & Theodora Crain respectively.
This is the fourth collaboration between Kate Siegel and Mike Flanagan since Oculus (2013), Hush (2016) and Ouija: Origin of Evil (2016).
Gerald saying "we should take our medicine" is a reference to the novel The Shining by Stephen King where Jack tells Danny to "take his medicine".
In Brazil, Stephen King's Dolores Claiborne novel/movie were named Eclipse and Total Eclipse.
Bruce Greenwood is fifteen years and seventeen days older than his on screen wife Carla Gugino.
This was Henry Thomas' first Stephen King project since Nightmares & Dreamscapes: From the Stories of Stephen King (2006).
The beer in the film was from Fairhope Brewery in Fairhope, Al. This brewery is located near where the film was shot on location.