The Fallout universe is set in a timeline that diverges from the real world in several key ways, including technology, events, and timeline from World War Two. While Fallout is set in the future, technology is based off of nuclear fusion and the society formed around it developed as an advanced retro-futuristic atomic age that's reminiscent of the USA in the 1950s. In particular was an emphasis on American exceptionalism, which continued until the Great War of 2077.
The Great War of 2077 only lasted for two hours, yet was a milestone event in the Fallout timeline as it collapsed the two superpowers at the time, the United States and China, and caused untold devastation far beyond the nuclear detonation sites. Most key events in Fallout are dated in relation to the Great War, and most of the games only take place one to two hundred years after the War because of the effects of the nuclear fallout that plagues the lands.
Fallout's Timeline Explained
Fallout 76 is chronologically the first game in the timeline, and takes place in Appalachia from 2102 onward. Unlike the other vaults, Vault 76 opened just 25 years after the Great War and the residents were mandated to rebuild the area, unlike other vaults that Vault-Tec used for all kinds of outlandish experiments. Due to the player's efforts in the area, it becomes a habitable place and people from all over the East Coast begin traveling to the region to settle there.
Fallout is set in 2161 in Southern California, 84 years after the Great War, and is chronologically the second game in the series but was the first Fallout game to be released. The player character is a vault dweller, kicking off the tradition of Fallout protagonists being vault dwellers. Fallout 2 is set in 2241 in Northern California, 164 years after the Great War, and is chronologically the third game in the series. This protagonist, also called The Chosen One, is notable for not being a vault dweller; they're instead a direct descendent of the Fallout protagonist, who established a village in Oregon.
Fallout Shifts Its Setting to the East Coast
Fallout 3 is set in 2277 in Washington, DC, 200 years after the Great War, and is chronologically the fourth game in the series. It's the first shift from the West to East coast of the USA, and follows the Lone Wanderer as they search for their father across Fallout's Capital Wasteland. Fallout: New Vegas is set in 2281 in the Mojave Desert, 204 years after the Great War, and is chronologically the fifth game in the series. Unlike the other entries, there isn't a massive leap in time between Fallout 3 and Fallout: New Vegas, though they do occur in different parts of the USA.
Fallout 4 is set in 2287 in Boston, 210 years after the Great War, and is chronologically the sixth and final game in the series. From the general pattern of release, players can speculate that Fallout 5 will take place sometime after Fallout 4 on the timeline, more than 210 years after the events of the Great War, and nearly 200 years after the first Fallout game. Like many other sequels in the series, Fallout 5 might be set decades after its immediate predecessor, taking place as many as 300 years after the Great War.
Despite the time jump, much of the landscapes and cultural stagnation will probably remain familiar thanks to the nature of the Fallout world. With a devastated world soaked in radiation, the difficulty in communication, mutations, and lack of any organized systems, 300 years after the Great War still very much counts as a recovering post-war world.
Fallout 5 is in development.