Historical institutionalism has steadily expanded its empirical scope and refined its analytical toolbox since it crystallized as a tradition of political analysis during the “new institutionalisms” debate. This chapter details the origins and evolution of historical institutionalism, placing particular emphases on the temporal concepts that inform its analytical toolbox. It begins with a discussion of historical institutionalims’s evolving relationship with other varieties of institutional analysis, before debating temporal concepts such as critical junctures, path dependence, intercurrence, and modes of gradual change. A third section identifies analytical, methodological, and empirical areas of potential growth.