Ellie Williams was born in the spring of 2019, by which time the Cordyceps brain infection had spread throughout the United States. Her mother was a nurse named Anna, although the identity of her father is unknown. On the day of her birth, her mother passed away. Before her death, Anna entrusted her closest friend Marlene to look after Ellie. However, Ellie did not meet Marlene until she was 13 years old.[9]

As a child, Ellie grew up as an orphan in an oppressive military quarantine zone in Boston, Massachusetts, with little knowledge of the world before infection.[10]

According to Ellie, at one point in her life, she drove a car,[11] and used a BB rifle to shoot at rats.[12]