Born to Joseph and Elizabeth (Smith) Peck in Rehoboth, Massachusetts, she married John Butterworth, son of a British captain in 1710. Mary Butterworth allegedly started her counterfeiting operation around 1716. According to those who would later testify against her, Butterworth used starched cotton cloths to produce counterfeit bills, rather than the metal plates used more commonly in counterfeiting.
Using a slightly dampened piece of starched cloth she was able to lift ink from a genuine bill. With a hot iron, she transferred a pattern from the cloth to a blank paper bill, then inked the pattern by hand with quill pens. The original cotton cloth was easily disposed of through burning, leaving no hard evidence of a crime. Butterworth allegedly organized her counterfeiting operation into a cottage industry, sternly overseeing the work of the entire family. At the height of her operation, she was reportedly selling counterfeit bills at half their face value.
Colonial authorities knew of an extensive counterfeiting ring operating somewhere in the Rhode Island area throughout the later half of the 1710s, and felt it was beginning to have a damaging impact on the entire colonial economy. In 1722 colonial authorities became suspicious of Mary Butterworth after her husband John purchased a large, expensive new home for the family.
On August 14, 1723 a trial was held in Newport, Rhode Island. One Nicholas Campe testified he passed two counterfeit Rhode Island bills he obtained through Butterworth. Two of Butterworth’s associates (her brother and his wife) turned state’s evidence and also testified against her. Ultimately though, the court dismissed all charges against her for lack of hard evidence.