Frances Cathcart was born in North Carolina in about 1751. The daughter of a prominent doctor, Frances and her siblings were had educational opportunities that were uncommon for young North Carolinian women of their time. Frances' father brought Daniel Earle, a noted religious figure, from England to the colony to tutor the Cathcart children. Frances married Samuel Johnston, a noted politician and future governor of the state in May 1770.

In 1774 Frances, her sister Margaret, and several of her sisters-in-law signed a women's nonimportation agreement which later became known as Edenton Tea Party Resolves. Frances Johnston later died in Martin County, North Carolina on January 23, 1801.