Summary: This paper examines the origins of philosophical pragmatism in the USA in the second half of the 19th-century and its development and use up to the Second World War. The story is told through the lives and ideas of some of the main originators, Oliver Wendell Holmes jun., Charles Saunders Peirce, William James and John Dewey. The core idea of pragmatism, that beliefs are guides to actions and should be judged against the outcomes rather than abstract principles, dominated American thinking during the period of economic and political growth from which the USA emerged as a world power. The paper suggests that the practical, commonsense, scientific approach embedded in pragmatism resonates with OR as practised and that much of pragmatism could be attractive to practitioners and academics alike.