This is the Assembled History taken from Journal 3, with additions and changes taken from the main series and other supplementary material.
WARNING! UNMARKED SPOILERS BELOW! YOU HAVE BEEN WARNED!
65 Million BC:
- Dinosaurs ruled (Until they didn’t)
30 Million BC:
- UFO crashes and forms valley that would become site of Gravity Falls.
1000 AD
- Native people evacuate in a hurry, describing area as “Cursed land”. They leave impressions of the Zodiac and Bill Cipher.
1837 AD
- Quentin Trembley III wins election by a literal landslide. He is soon impeached due to rampant silliness.
1842 AD
- June 18 - Gravity Falls is founded by Quentin Trembley after he fell into it riding his horse backwards. He is later deposed and replaced by local nobody Nathanial Northwest by US Government.
1849 AD
- Gold Rush
1850 AD
- Lesser known “Flannel Rush”
1851 AD
- Mining ceases after miners claim sightings of prehistoric beasts.
1862 AD
- Mabel and Dipper spend a short while in this era while time travelling. They meet the Mecc family of pioneers, who would later be credited with the invention of the "High Five.".
- Nathaniel Northwest tricks the people of Gravity Falls into building the Northwest Manor.
1863 AD
- Northwest Family commissions town lumberjacks to build their mansion in exchange for invitations to their party. Construction and subsequent reneging on said deal results in the Mud Slide of ’63, leading to numerous deaths. One lumberjack would swear vengeance on the Northwest Family.
1883 AD
- Great Train Crash of ’83, caused by conductors distracted by “Flash of light”, sending train off a cliff.
1909 AD
- Eustace Befufftlefumpter is born.
1912 AD
- Eustace Befufftlefumpter is elected mayor of Gravity Falls.
1920 AD
- Maple syrup prohibition leads to secret Pancake Speakeasies.
1937 AD
- Plane crash in mountain. A woman escaped into the forest, leaving “Amelia was here” carved in mountainside.
1947 AD
- UFO sighted headed east. Ronald Sprott Sr. claims to have shot it with his shotgun.
1951 AD
- June 15th - Stanley and Stanford Pines are born.
1960 AD
- Greasy’s Diner salvages crashed train parts for restaurant.
1969 AD
- Stanford Pines is nominated for Westcoast Tech. However, an accident caused by his brother Stanley ruins his admission.
- Stanley is disowned by his family. He forms “StanCo” and is later forced to flee New Jersey from unsatisfied customers.
- Stanford enters Backupsmore U.
1975 AD
- Stanford is accepted into a doctoral program and is granted a research grant for a field of his choice, choosing to study the anomalies in Gravity Falls.
- June 18 -Ford arrives in Gravity Falls and begins research. His studies take up three Journals.
1981 AD
- Stanford meets Bill Cipher after finding cave drawings left behind by the native peoples.
- Bill convinces Stanford to build Universe Portal, and to let Bill into Stanford’s mind whenever he wants.
- Fiddleford McGucket comes to Gravity Falls to help build Portal. An encounter with the Gremloblin leads to him creating the Memory Ray.
- The Bunker is built, and the Shapeshifter is found and confined.
1982 AD
- January 18th: During the first test of the Portal, McGucket is almost pulled in completely. After Ford refuses to destroy the portal, he leaves the project and forms the Society of the Blind Eye. However, McGucket's constant overuse of the memory gun on himself steadily causes him to degenerate into "Old Man" McGucket.
- Stanford learns of Bill’s deception and hides Journals 2 and 3. He writes to Stanley to help hide 1.
- Stanley arrives in Gravity Falls. A fight with Stanford results in the latter being sucked into the Portal completely, leaving only 1 to guide Stan.
- Stanley takes Stanford’s identity and starts the Mystery Shack. He later stages a car crash to kill off his own name.
1990 AD
- July 13 - Jesus “Soos” Ramirez is born.
1995 AD
- Ma and Pa Duskerton die of sudden heart attacks after witnessing teenagers with "boomy boxes and disrespectful short pants."
1996 AD
- Wendy Corduroy is born.
1999 AD
- August 31 - Mason “Dipper” and Mabel Pines are born.
2002 AD
- Gideon Gleeful is born.
- July 13 - Soos is hired as Mystery Shack handyman.
2012 AD
- Wendy takes a summer job as Mystery Shack Gift Shop cashier.
- Gideon finds Journal 2 and starts Tent of Telepathy.
- May - Dipper and Mabel begin their vacation in Gravity Falls.
- June 1 - Dipper finds Journal 3.
- July - Gideon attempts to take control of Mystery Shack. In the resulting battle, Stan exposes his fraud and secretly takes Journal 2. Dipper shows Stan 3 soon after. Gideon goes to jail.
- July 20 - Stan uses Journals 1, 2, 3 to activate the Universe Portal. Agents Powers and Trigger detect energy spike and begin investigating Gravity Falls.
- While searching for the Author, Pines Twins shut down the Society of the Blind Eye.
- At Northwest Party, the Lumberjack’s ghost appears as promised. With Dipper’s help, Pacifica Northwest fulfills the Promise, putting the ghost to rest.
- August - Stan is caught stealing nuclear waste to power the Portal by the agents. The Pines escape custody just in time for the Portal to bring back Ford Pines. Ford uses the Memory Ray to trick Powers and Trigger into closing their case and leaving town.
- Ford contains the Rift created by the Portal.
- Mayor Befufftlefumpter dies. Tyler Cutebiker is elected mayor.
- Ford, with Dipper and Mabel’s help, create a magic barrier around Mystery Shack as a defense from Bill.
- August 23 - Mabel is tricked by Bill into breaking the Rift’s container. Weirdmageddon begins.
- August 25 - Weirdmageddon ends when Stan tricks Bill into entering his mind so Ford can erase them both with Memory Ray. Stan spends the next week recovering his memories.
- August 31 - Dipper and Mabel turn 13. Stan puts Soos in charge of the Mystery Shack.
- September 1 - Both sets of Pines Twins leave Gravity Falls to pursue new adventures.
3012 AD
- Time Baby awakens and conquers the universe. He later forms Time Police.
- The world ends, as predicted by an all-knowing mailbox.
Distant Future (c. 207̃012 AD)
- Blendin Blandin is arrested for misuse of his Time Tape. He later escapes and challenges Dipper and Mabel to Globnar.
- Dipper and Mabel win Globnar and award Blendin his freedom and previous job.
