Though born in Woburn, Massachusetts, in America, Rumford moved to London in 1776 and began investigating gunpowder. He was knighted in 1784, and became an aide-de-camp to the Elector of Bavaria. He spent eleven years in Bavaria, reorganizing the Bavarian army and establishing workhouses for the poor. In 1791 he was named a count of the Holy Roman Empire.
His most important scientific work took place in Munich, and centered on the nature of heat, which he demonstrated in "An Experimental Enquiry Concerning the Source of the Heat which is Excited by Friction" (1798) to be not a liquid form of matter but a form of mechanical energy.
Rumford was an active inventor, developing improvements for chimneys and fireplaces and inventing the double boiler, a kitchen range, and a drip coffeepot. Furthermore he was socially active as founder of Munich's English Garden (German Englischer Garten) in 1789.
With Sir Joseph Banks, he established the Royal Institution of Great Britain in 1799; the two chose Sir Humphry Davy as the first lecturer. He endowed the Rumford medals of the Royal Society and the American Academy of Arts and Sciences, and endowed a professorship at Harvard University.