Fallout 3: Escape From Vault 101

Gamasutra has published an interesting article called "Escape From Vault 101" that analyzes many of the decisions Bethesda Softworks made during the development of Fallout 3 - like why they decided to place bizarre NPCs like The Mechanist and The AntAgonizer in the wasteland.
The decision to set Fallout 3 in D.C. was ostensibly made to further distance Bethesda's game from the West Coast adventures of Fallout 1 and 2, and because the Maryland-based developer were more familiar with the Capitol. This is workmanlike reasoning, which doesn't hint at the massive implications the decision would have on the creative direction of the game.

It's not until after the player leaves the pristine sanctity of Vault 101 in search of his father -- and makes it to Washington proper -- that you remember what's specifically important about D.C.

Not until you march down the Mall, through the wrecks of the Washington Monument, the Capitol Building, the Museums of History and Technology, the National Archives and the Lincoln Memorial to the tune of the America the Beautiful, ducking the street-gangs and mutants further blowing apart the ruins, can you can tell that this is the dismal coda to American history.

America as it was conceived in 1776 is in gradual decline. While some civilians still go about their lives, it seems inevitable that the light will blink out sooner rather than later. When you're able to casually scavenge the Declaration of Independence, and sell it, whatever immaculate prestige American history once had is probably gone.