President's Key

The President's Key is an item that is presumably handed down to each president of the United States. The key was last held by Quentin Trembley, until he was kicked out of office, and disappeared with it. The key has the incredible ability to open any lock in America.

History
The short-lived eighth-and-a-half president Quentin Trembley was given the key when he became president. However, his presidential term showed off his inherent insanity, and he was thus kicked out of office. He was able to escape to a small valley in Oregon, where he would found the town of Gravity Falls. The key was lost with him.

Years later, his body, preserved in peanut brittle, was uncovered by Dipper and Mabel Pines. Sheriff Blubs and his Deputy, however, had been ordered to detain them, in order to keep the nation's greatest embarrassment a secret. They took the president and the twins by train to Washington, D.C. However, on the way to the city, Mabel accidentally helped the former president escape from his hibernation. Realizing they were in a crate, he attempted to use the key to escape, to no avail.

After they escaped, Trembley handed the key to Dipper, telling him to go unlock America's secrets. Dipper was able to use the key to unlock his Grunkle Stan from the stockades in which he had been placed.

Use
The President's Key functions similarly to a skeleton key, in that it can be used to open any lock, regardless of shape or size. However, from Trembley's wording, it can be inferred that it is mildly limited in that it can only open locks made in America.

Dipper was able to successfully test the key, breaking his great-uncle out of the stockades.

Trivia

 * The President's Key could very well end up being used as a "Chekhov's Gun": A seemingly irrelevant item introduced early in the story, but proving to be of great significance or use later in the story.