This small settlement literally sprung up around the severed head of Lincoln, a portion of the statue from the Lincoln Memorial, and a random block from the memorial’s inscription. How it arrived in this remote spot is any-one’s guess, but the Temple’s residents now revere the head as a symbol of the Abolitionist movement. The entire compound is a haven for freed slaves and anti-slavery activists.
The temple's leader, Hannibal Hamlin, dreams of a safe haven for would-be slaves, away from the slavers. Their respect of Abraham Lincoln is almost reverent, and they wish to set up their temple in the Lincoln Memorial - not only because it would be easier to defend, but because he is known to them for freeing all men from slavery in America. Because of this, Hannibal Hamlin will offer to buy any of Lincoln's artifacts.
The Temple of the Union is located northwest of Canterbury Commons. There are several ways to get its marker on your map. You will be given the marker if you help out Mei Wong in Rivet City or by successfully removing a collar from a slave in a random encounter. You can also find a map on the several corpses of a dead slave, presumably a failed runaway.
It is a ruined two-story building that houses a group of escaped slaves. Initially, Abraham Lincoln's Head is here, although it is unclear how it got here. It is possible that it was being repaired or stolen. Completing the quest Head of State will result in the head being moved to the Lincoln Memorial.
The name "Temple of the Union" comes from the words above Lincoln's statue at the Lincoln memorial. The passage reads, "In this temple, as in the hearts of the people for whom he saved the union, the memory of Abraham Lincoln is enshrined forever." On the block Caleb is working on, the words "Temple of the Union" are visible, with the others faded out. Presumably, the block arrived at the building at or around the same time as the statue's head.
Fast travel is disabled when in the Temple or nearby surroundings.
Although Bill, Simone, and Alejandra can be enslaved, firing the Mesmetron inside the Temple will permanently make everyone go hostile.
The Temple is a location for a Fallout 3 random encounters|random encounter, but only if the slaves have been moved to The Lincoln Memorial or you helped the slavers kill the slaves. The most notable is some Talon Company mercs spawning inside the temple, even with the gate closed. (It may be necessary to leave the gate open in order to trigger the random encounter.)
There is a Vertibird landing zone on an elevated highway near the Temple. It occasionally drops off a number of Enclave soldiers, and battles often break out between them and the raiders who occupy the open shack on the highway. There are also a few skill books in the shacks on the elevated highway.
After talking to Hannibal and not swearing your loyalty to the Temple, you are "locked" inside until you do. Hannibal doesn't seem to realize that the player can jump out of one of the many windows.
Dogmeat is able to open the door shortly after the player is locked inside the Temple.
If you are seen picking the average lock to the Storeroom, everyone inside the Temple will become hostile.
If you walk back outside after talking to Simone but before she shuts the gate you will be locked out; Simone only replies that Hannibal is waiting and will not open the gate again. You can, however, ring the doorbell located under the "Ring Me" sign, or pick the gate (Very Hard lock).
Many of the items inside the temple are considered owned, even if the slaves move or are killed.
One of the members will say that you cannot leave, however, nothing will happen if you leave anyway.
Behind the scenes
The inhabitants are named after members of Abraham Lincoln's cabinet. Hannibal Hamlin was Vice President, Caleb Smith was Secretary of the Interior, William "Bill" Seward was Secretary of State, and Simon(e) Cameron was Secretary of War. The dog, Four Score, is named for the opening words from Lincoln's Gettysburg Address (Four score and seven years ago, our fathers brought forth on this continent...)
The name of the Temple is based on the federal government of the United States during the American Civil War. (See: The Union)
The Temple of the Union appears only in Fallout 3.
↑Fallout 3 Official Game Guide Game of the Year Edition p.333: "This small settlement literally sprung up around the severed head of Lincoln, a portion of the statue from the Lincoln Memorial, and a random block from the memorial’s inscription. How it arrived in this remote spot is any-one’s guess, but the Temple’s residents now revere the head as a symbol of the Abolition-ist movement. The Temple is a reasonably fortified ruined building; you're been greeted by Simone Cameron, a no-nonsense sentry wanting to know what you're doing here. Remain polite to enter the premises. She gives you a Key once she deems you trustworthy. Or you can unlock the front gate yourself. This usually leads to violence. You're told to meet with Hannibal before the Abolitionists will begin to speak freely with you. To remain on friendly terms, swear to protect the Temple of the Union. You are given the Temple of the Union Key as a symbol of their trust. You can now freely talk to all the Temple's inhabitants and explore their base. All the Abolitionists have Temple of the Union Keys to get in and out of the place. Caleb and Hannibal are also carrying a Storeroom Key. Conclude Miscellaneous Quest: Head of State favorably with the Abolitionists, and you receive Dart Gun Schematics."