Manx's map of Inscapes shows the location is "Pennywise Circus" which is a reference to "It", a novel written by Hill's father Stephen King.
The Inscape map shows the location of "The Treehouse of the Mind", which is from another of Joe Hill's books, Horns.
Lovecraft Keyhole on the map isn't just a reference to H.P. Lovecraft but also to Joe Hill's Comicbook Series with Gabriel Rodriguez Locke & Key which takes place in the town of Lovecraft and is about magical keys.
Also on the map is a place called Lovecraft Keyhole, a reference to H.P. Lovecraft, a Horror writer and native of Rhode Island.
RISD stands for the Rhode Island School of Design in Providence, Rhode Island, the state capital.