Though there are numerous recent works on the almost endlessly definable topic of US imperialism, Ian Tyrrell's new book finds something of a blind spot in the existing historiography. Tyrrell identifies moral reform as a part of America's formal and informal imperial endeavours that has received relatively scant attention, aside from a few specific case studies. Therefore his book aims to place the subject within a wider context, exploring the efforts of America's “moral reformers” and their contribution to US “cultural hegemony” abroad (3). These reformers represent a mixture of humanitarian groups almost as varied in motivation as the progressive movement itself, including prohibitionists, evangelicals and even the International Anti-cigarette League. Despite a focus on the reformers, Tyrrell makes it clear from the outset that this is not a book exploring the passive reception of moral exports, but rather one that deals with transnational interactions. For the author it is the “complicated dialectic between the national and the transnational” that lies at the heart of his book (7).

The book is divided into four sections – each further subdivided into chapters – that run in very loose chronological progression. The first section of the book presents the late nineteenth century as a period of ever-growing cultural exchange and communication across national borders. Within this context the voluntary, moral-reform sector was, Tyrrell argues, creating a “public space” internationally (24). The book's second section documents the growth of these moral reform organisations in coordinating humanitarian aid in countries across the globe. The author presents American relief missions as a “networked constellation of reformers,” which became entangled in the world of European imperialism (73).

In the third section, the period of American overseas annexations comes more directly into focus and the author touches upon the complications of the United States becoming a “formal” empire. It looks at how moral reformers coalesced to try and keep American imperialism exceptional, while seeking to better the lives of their nation's new wards, particularly those in the Philippines. Liquor, opium and prostitution gave these reformers a number of causes to strive against in the colonies, while others, such as anti-lynching campaigner Ida B. Wells, campaigned from the outside to try and make the United States begin their reform efforts on the home front.

The last section of the book turns to the final rise and abrupt fall of the American moral reformers as they repositioned themselves as world leaders. Tyrrell identifies the movement's Achilles heel as the fact that they became tied too closely to the fate of their flagship anti-alcohol campaign, which began to founder as the 1920s came to an end. Overall, the book brings together fascinating analyses of personal and organizational tales that complement the broader narrative of America's role in world events. It also brings a much-needed focus to both inter- and transnational exchanges during this period, whilst illustrating the very real impact of these “moral reformers” – in their many guises – on the development of US imperialism at the turn of the century.