Peter Baldwin is especially interested in the historical development of the modern state—a broad field that has led him in many different directions. Two aspects of his work unify it. First, he has attempted to understand contemporary issues from a long historical perspective, whether that be the class coalitions that cemented the modern welfare state, the 19th century public health strategies that provided the template by which the AIDS epidemic was fought a century later, the battles over intellectual property stretching back three centuries that inform, indeed determine, our current battles over copyright, downloading, and internet piracy, or the ever-growing role of law as the socializer of last resort in modern society. Second, he has studied the development of the state transnationally, using detailed and often archival sources in half a dozen languages to marry a broad comparative approach to rigorous empiricism. His books have dealt, above all, with France, Germany, Britain, Sweden, Denmark, and the United States. He has published works on the comparative history of the welfare state, on social policy more broadly, on public health, and on the history of copyright. Other interests have included Nazi Germany and historiography. His latest book is a global history of the development of law and crime over the past 2000 years. He has forthcoming books on open access and on the COVID-19 pandemic.