This introduction considers the highly influential contribution of Douglass C. North to economic history and institutional economics, as it developed from the 1960s until his death in 2015. It sketches the evolution of his arguments concerning the roles of institutions, organizations and human agency. North’s conception of the economic actor became progressively more sophisticated, by acknowledging the role of ideology and adopting insights from cognitive science. Eventually he abandoned the proposition that institutions are generally efficient, to propose instead that sub-optimal institutional forms could persist. A few noted criticisms of North’s work are also considered here, ranging from those which are arguably off the mark, to others that retain some force. The contributions to this memorial issue are outlined at the end of this introduction.