Worked as a blacksmith, soldier, and storekeeper. Designed a steam-propelled boat (c. 1784-87); competed bitterly with rival inventor John Fitch for patronage and patent rights. Visited Philadelphia and presented his design to the American Philosophical Society (spring 1788). Franklin and others formed a “Rumseian Society” and sent Rumsey to England to obtain a patent and raise capital. Published two pamphlets on steam power and considered its application to engines, boilers, and saw and grist mills.
Son of Edward and Anna (Cowman) Rumsey of Cecil County, Maryland. Married (2) Mary Morrow; had issue. Died in London.