Hannibal Hamlin, born in 2234, is an ardent abolitionist, stemming from his 23 years as a slave before he fled his captors at age 37. He has spent the six years since then doing everything in his power to help escaped slaves and fight the scourge of slavery. Three years ago, he found the head of Lincoln's statue and established the community of the Temple of the Union. Each day, Hamlin delivers antislavery speeches to its people.
Head of State: Hannibal asks the player to check the Lincoln Memorial for super mutants and to get the Lincoln Memorial poster for Caleb. When you arrive at the Lincoln Memorial, you'll find that it's inhabited by Slavers. At this point, you can either tell Hannibal about the slavers or turn him (and the other Temple of the Union slaves) in to Leroy Walker. If you tell Hannibal about the slavers, he'll ask you to kill them; and after killing them, you can tell him it's safe to go to the memorial. As a reward, he'll give you the dart gun schematics.
“Let me tell you the story of Abraham Lincoln. He was born a Tucky Tearsman. The truth of this mysterious title has been lost, but we know it was a great honor. As a child he could not bear to see any animal chained or imprisoned. He was even known to set free the family Brahmin on occasion. As a youth, Abraham Lincoln fought Raiders in the war of the black hawks. When the war ended, he settled down to rule the Linoy, a small tribe of free men. He grew so famous that one day he was made President. He ruled over all the land. When he declared that all slaves must be freed, the slavers rebelled against his rule. They fought a great war, which Lincoln won. When he came to free the slaves, an assassin of the slavers struck him down. In the confusion, a few of the slavers escaped. Lincoln's generals hunted them, but could not find them. The bombs ended the era of Lincoln, but we will resurrect his voice. We will restore the greatness of his vision where all men are created equal, and all men can live free!”
↑Fallout 3 Official Game Guide, page 43: "There is a band of abolitionist slaves deep in the Wasteland. They are all escaped slaves, seeking to end slavery for all time. You can learn more about them in Miscellaneous Quest: Head of State."