The United Kingdom has been weakening, and this book helps to explain why. Alvin Jackson examines the UK in the light of the experience of similar union states elsewhere, offering the first sustained comparative study across the long 19th century and beyond. The UK was not in fact the only self-styled 'united kingdom' of the time: Jackson argues strikingly that Britain exported the idea of union through the advocacy or encouragement of other multinational united kingdoms at the beginning of the 19th century. The work is distinctive in its geographical breadth. Jackson draws together the histories of Ireland, Scotland, Wales, and England and explores the links between them and Sweden-Norway, the united Netherlands, Austria-Hungary, and Canada-and many other polities across the globe. United Kingdoms looks too at the institutions and agencies affecting the strength of union-from monarchy, aristocracy, and religion through to class, money, and violence. Jackson offers new overarching arguments about the origins and survival of all union states, and in doing so, sheds new light on the particular history and condition of the UK.