The child of a prominent physician, Dr. Richard Bayley, who was first Health Officer in New York City. At the age of 20 she married William Seton, and had 5 children with him. In 1797 she was one of the founders of the Society for the Relief of Poor Widows with Small Children which was the first charitable organization in New York. Her husband suffered bankrupcy and poor health, so the family travelled to Italy in 1803 where he died of tuberculosis. When she returned to New York, she converted to Catholicism and was shunned by most of her friends and relatives. Consequently she had trouble earning a living.