Sarah Vandyke was born around 1843 in New York. She grew up and attended school in Cherry Valley, New York. In 1850, she was living with George and Elizabeth Milson, who may have been her uncle and aunt. A decade later, she was working as a domestic servant for an elderly tailor named Daniel Robinson. By 1870, she was living with her aunt Sarah Frances, an English immigrant who owned $11,500 of real estate and $2,100 of personal property. Sarah apparently never married. By 1900, she was living with her cousin Elizabeth Milson in a rented house in Cherry Valley. She died sometime after 1900.