It has become more common to think of the United States as an empire. Although some “empire deniers” persist, they face an increasingly loud chorus of post-revisionist scholars, pundits, and even officials who are willing to entertain the idea that the United States is and always has been imperial. This book joins that chorus, but it has also sought to push further, dig a little deeper, and look more widely. Rather than seeking a warrant to call the United States an empire, this book has put America's imperial formation in comparative light. It has examined differences and similarities between America's imperial practices, forms, and dynamics on the one hand and Britain's imperialism on the other. The United States is and has been an empire; this book has examined its differences and similarities with its predecessor.