When Mary Mills was born on 20 February 1763, in Jamaica, Queens, New York, United States, her father, Rev. William Mills, was 23 and her mother, Mary Reading, was 26. She married Dr. Robert Halstead on 1 October 1787, in Elizabeth, Union, New Jersey, United States. They were the parents of at least 4 sons and 1 daughter. She died in 1798, at the age of 35.