National Guard Depot

Located along the northern edge of Downtown DC, the National Guard Depot is a high-security compound that used to be the headquarters for the Washington militia. It can be reached from the wasteland, avoiding the metro system. An easy way to find the Armory, is to head directly south from Vault 108, or from the Robot Repair Center. (Directly north of Vault 108)

National Guard Armory
The Armory is only accessible after traversing the National Guard Depot, the National Guard Training Wing, the National Guard Depot Offices, then exiting from the Offices back to the National Guard Depot (update - you can also reach the switch from jumping on a slope in the mid level of the room). Just as you exit back into the Depot, there is an electrical switch about 15 feet to your left. This will unlock the Utility Door two stories below you, which in turn allows you to enter the Armory. (The utility door cannot be lockpicked, even though it is shown with a Very Hard lock). BUT, be careful, there is a sentry bot or a mister gutsy right inside. Activating the second switch inside the utility room will open a trap door that leads into the Armory itself.

National Guard Bunker
The bunker, accessed through the armory, is opened by completing the unmarked quest Keller Family Refuge. Inside the bunker is the Experimental MIRV Fatman (and a plasma grenade hidden in a cooking pot on the first set of shelves left-hand side.) Also 5 Mini Nukes next to MIRV and a Nuka-Cola Quantum in a bin near the back. You may also come across a Glowing One inside.

Inhabitants
The National Guard Depot is mainly inhabited by Sentry Bots, Mister Gutsys, Protectrons, and Robobrains.

Depot

 * Nikola Tesla And You located in the National Guard Depot, in a storeroom on the lowest level (If you stand in front of the "Very Hard" door leading to the armory it is the storeroom directly to your right in one of the shelves.)
 * Pre-War Book: two located in the National Guard Depot on the third floor, right in front of you if you go up the stair you see on your left after you enter from The Capital Wasteland.

Training Wing

 * Tales of a Junktown Jerky Vendor.Take the staircase, located through a door in the eastern-most section of the hallway with the american flags, and keep going until one arrives in a room with a standard metal/grey desk. You will be facing the desk when you enter the door at the top of the stairs. It is on said desk.
 * A safe in the adjacent room as Tales of a Junktown Jerky Vendor. You walk through a collapsed section of wall from this room to the room with the Average Locked safe.
 * Safe may contain a Stealth Boy.
 * Pre-War Book in the room after the Tales of a Junktown Jerky Vendor (above the safe).
 * Random weapon along with ammo. Found in one of the 2 wooden gun cabinets in the same room as the 2 books above (Pre-War Book and Tales of a Junktown Jerky Vendor).
 * Stealth Boy in a center set of 3-lockers just before the double-doors that lead to the shooting range. When facing the double-doors, it's in the middle set of 3 on the left. (NOTE: This is random.)
 * About 4 Combat Helmet and 6 10mm SMGs and 6 Assault Rifles in the room after the hallway with the patrolling Sentry Bot, right before the locker room leading to the shooting range. The weapons and helmets are in the wooden shelves behind the counter with 2 non-working terminals.

Offices

 * Duck and Cover! located on a long counter in an irradiated section of the National Guard Offices portion.
 * Three more Pre-War Books in the National Guard Offices on the shelves in the center of an open collapsed two floor room, one level above the long counter in an irradiated section as mentioned above.
 * Stealth Boy in an average wall safe, on the first floor of the Training Wing. (Random chance, as with most loot from safes.)

Armory

 * You've just hit the Mother-loving mother-lode.
 * Five Mini Nukes and the unique Fat Man "The Experimental MIRV".
 * The Bobblehead: Small Guns located on a shelf in the sealed storage room in the basement of the Armory.
 * A Nuka-Cola Quantum underneath the table, inside of the small bin, next to the refrigerator within the Keller shelter.
 * Four Assault Rifles and 5.56mm Round ammunition.
 * Missile Launcher and ten Missiles.
 * A Minigun and 5mm Round ammunition.
 * Two 10mm SMGs, two 10mm Pistols and 10mm Ammo.
 * Lots of Rad-X, RadAway, Stimpacks, and some Buffout too.
 * Several bottles of Purified Water.
 * A copy of U.S. Army: 30 Handy Flamethrower Recipes on the same table as the M.I.R.V.
 * All of the ingredients for a Nuka Grenade are located within the bunker (Nuka-Cola Quantum, Tin Can, Abraxo Cleaner and Turpentine) so using the Workbench the player can craft one as long as they have the schematics.
 * Four Pulse Grenades and four Pulse Mines.
 * Two Combat Armors and four Combat Helmets.
 * Two Radiation Suits.
 * A Plasma Grenade in a large pot on a shelf.

Outside

 * Four ammo cases in a military truck in the parking lot
 * Nuka Cola machine right outside the entrance
 * A patrol of Brotherhood Outcasts will spawn outside of the fort next to the trucks outside of the parking lot
 * To the north of the armory, amongst the destroyed houses is what appears to be a single 10mm pistol lying next to a burnt skeleton. However, it is actually a stack of 7 identical 10mm pistols. The house containing these pistols is first house north-east of the playground area.
 * If you head due west from the Depot entrance, staying on the road heading downhill, as you reach the intersection just south of the Rock Creek Caverns (a very brief walk from the Depot), you may be ambushed by Super Mutants and Raiders, possibly depending on your level.

Glitches

 * You can get to the higher level of the top floor by stacking barrels. However, it's very hard to do (you need at least 5 barrels) and there's nothing up there but an empty suitcase and an open safe, unless you want to just jump off the top which teleports you to the 4th floor - the same as if you go through Vault 87's Vault door.
 * You can get inside the bunker without getting the transcripts. To do so, walk into the corner made by the door and bunker access terminal. Then crouch, go into third person view, and twirl the camera around until it says "activate electrical switch". The trigger is very small, but should appear on the door or the door frame, a little higher than the player's head. Activate it, and the bunker door will open. This is a brilliant time saving method and should be used if you don't want to bother hunting down the transcripts. (Confirmed on PS3, PC and 360)
 * On one of the upper levels that isn't connected to the switch room there is a pile of rubble in which the floor fell in, simply drag a barrel over to it, put it sideways and jump on the rubble (you may need to crouch to get past it to the top floor) once on the very top floor drop through the hole in the ceiling over the switch room and voila
 * Sometimes when you're going back and forth from any location to the fort, your game may freeze on the loading screen and you would have to restart you console to load the game again. NOTE:reloading when the game start will not allow you to enter the armory again. (360)
 * After having destroyed the two Protectrons out front, upon fast traveling to the Depot from somewhere else, the two of them will fall from the sky still destroyed.
 * There is a way to get to the top of the National Guard Depot building by only having to use two barrels. The player has to go to the middle of the fourth floor then go to the fallen radio tower and the caved in ceiling. From there the player has to put a barrel on the radio tower and jump on it from the collapsed ceiling then you will be on the fifth floor. The player then has to go to the inaccessible stair case with the emergency lights. Then the player needs to put a barrel on the glitch of rubble by the collapsed cubicle, then jump on the tallest corner of the collapsed cubicle then jump on the barrel and jump on the top floor (frequent saving is recomended).
 * It is possible for a character with high Agility to skip the Training Wing and Depot Offices, going straight to the Armory. Locate the staircase in the middle of the eastern wall of the National Guard Depot, and climb to the top. From there, head due west past the fallen steel truss, around or over the gap in the floor, and go through the open doorway. Straight ahead is a pile of fallen floors or walls blocking another staircase. By jumping up the left side of this rubble, and then crouching once you're up, its possible to climb the rubble and stairs to gain access the the highest level of the building. From there, head to the far southeast corner where you can jump down to the electrical switch near the exit to Depot Offices. Activate the electrical switch and jump down to the Armory doors. (360)
 * Be careful climbing on overturned desks to jump or you'll fall in the middle and get stuck in the legs and have to reload, which is most inconvenient. (360)

Appearances
appears only in Fallout 3.

YouTube Videos
A faster way to open the Armory door WWf2XelJzOs


 * Getting inside the bunker without the transcripts

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