He was born in German Ansbach to French parents, apparently lived in Switzerland for a time, and moved to the Netherlands around 1750.
When John Adams became minister plenipotentiary to Holland, Dumas acted as his secretary and translator.
When Adams went to Paris, Dumas acted as chargé d'affaires ad interim from the United States.
[2] In 1775, Dumas devised the first diplomatic cipher used by the Continental Congress and Benjamin Franklin for secret correspondence with agents in Europe.
[4] In 1776, Dumas contacted officials in Holland, Spain and France seeking trade in badly needed materials for the United States.