Eliza was an Afro-American servant, who, along with her father, Abraham, was employed by William M. Tweed during the American Civil War. When her father was killed during the New York City draft riots, she vowed to avenge him and joined the Assassins, whom she had learned about through Varius.
In 1863, through Eagle Vision, Eliza discovered the content of a letter detailing the Templars' plans for the draft riots and worried for his safety, went to find her father who had been sent to deliver that same letter. The letter mentioning the Aztec Club, she went there where she witnessed a fight between the Assassin Varius and Templar Cudgel Cormac for a dagger–a part of the Trident of Eden–with the latter managing to escape with the artifact. Eliza came to the aid of Varius, who had been paralyzed, and, in exchange for his help in locating her father, revealed what she had learned about the Templars.
The pair left for Tweed house, with the Assassin teaching Eliza the basics of freerunning after noticing she was naturally gifted. He also offered to introduce her to the Brotherhood. Arriving at Tweed's house, a distraught Eliza discovered that while also looking for her, Abraham had been beaten by thugs during the riots and was on the brink of death before he died in her arms.
At this point, Cudgel appeared to hand the stolen artifact to his Grand Master, but Varius interfered and the two become embroiled in a fight once more. Following them on the city' roofs, Eliza witnessed Cudgel using the Trident prong's powers to overpower Varius, stabbing the confused Assassin in the stomach. However, before he could deliver the final blow, Eliza used his own air rifle to hit him with a paralyzing dart and took the prong. Although she ended up sparing Cudgel, she vowed to join the Assassins and stop the Templars' machinations. Eliza subsequently brought Varius to a hospital with the help of Tommy Greyling and Adelina Patti.
Eliza later fought during the Civil War and completed Varius' original mission, giving the artifact to Ulysses S. Grant. She also completed her Assassin training with Varius, the two Assassins spending a lot of time together as a team and becoming close. Eliza was the one who brought forward evidence of Grand Master Tweed's corruption, leading to his arrest in 1871.