Trembley's Cove is a hidden location underneath the Gravity Falls Cemetery, accessible by pulling up on the pointer finger of an angel statue above. It contains many secret historical artifacts, mainly documents, including one showing that Abraham Lincoln had a hand growing out of his head, which was the reason he wore his hat, and another revealing that Benjamin Franklin was a woman.
In "Irrational Treasure," Dipper and Mabel set out to uncover the truth as to whether or not Nathaniel Northwest was the true founder of Gravity Falls, Oregon. After following a series of clues, the twins find the entrance to the cave, triggered by a statue's finger, thanks to Mabel pretending that the statue was picking her nose. The two descend a set of stairs revealed by the lever and, in an underground corridor, accidentally set off a trap that shoots tranquilizer darts at them; they quickly run through and make it to the end of the tunnel unharmed. There, they find many artifacts and documents on historical secrets, including the one they are searching for, the Northwest Cover-up. They read the document and learn the identity of the real founder of Gravity Falls: Quentin Trembley.
Soon after, Sheriff Blubs and Deputy Durland arrive, finding their way by following Mabel's trail of discarded candy wrappers, and confront the twins. However, they are delayed by Durland's fainting, due to being hit with an excessive amount of darts. After Durland awakens, he and his associate show Dipper and Mabel a film regarding Trembley, showing how he won the election in a literal landslide and did such a great number of silly and "shameful" acts that he was removed from office. Then, the film shows him fleeing to an uncharted valley which he named "Gravity Falls" after plummeting into it at high speed. The documentary then ends, and Sheriff Blubs shows the twins Trembley's body encased in a block of solid peanut brittle. Blubs and Durland then ship the twins, Trembley and the artifacts on a train destined for Washington, D.C.