Frymer begins by asking his reader to consider a map of the continental United States. The image, he suggests, is both “familiar and natural” (2), so much so that it can seem as though the country was always destined to take this shape. Conventional narratives often give the history of US expansion a providential air – a spontaneous movement of intrepid settlers forging westwards, taming the wilderness as they went. Building an American Empire challenges this satisfying myth. Adding his voice to a growing chorus of Western and borderlands historians, Frymer exposes US continental expansion over the long nineteenth century as a “lengthy, diverse, and contested project,” contingent upon a multitude of political, geographic, and social factors. There was nothing inevitable, he argues, about the present shape and size of the United States.

Frymer's main contribution is his focus on the federal state, which, he argues, was a critical factor in determining the rate and scope of American expansion. Building an American Empire therefore “complicates long-standing narratives of the ‘weak’ antebellum American state” (11), and instead makes the case for an active federal government – one aware of its limitations (an underdeveloped bureaucracy and military), but willing to use what powers it did possess in creative ways. Nowhere was this better demonstrated than in federal land policy, which policymakers used to acquire, survey, sell, and incorporate new land to regulate the pace and scope of national expansion.

Building an American Empire divides into two broad epochs. The first spans from Independence to the 1840s, a period when the federal government directed the settlement and incorporation of new territory in a manner commensurate with its ability to defend it. The Treaty of Paris in 1783 and the 1803 Louisiana Purchase, for example, brought US borders into the orbit of the Spanish and British American empires. Conscious that impatient settlers might drag the United States into a conflict with these rival powers by encroaching on their colonial possessions, US policymakers prohibited settlement on unsurveyed territory and established residency quotas for land ownership in order to control migration and settlement at their nation's peripheries. During the 1830s and 1840s, as the US population grew, legislators lifted these restrictions to encourage migrants to settle in more distant regions in the Southwest and along the Pacific coast – a means to assert US sovereignty in these far-flung places without the expense of military occupation. Federal land policy, then, reflected both the ambition and the realism of those who designed it.

There is a change of register in the last three chapters, which cover the 1840s through to the early twentieth century. During this time, as the nation-state evolved in size and strength, Americans grew confident in their hegemony on the continent. Federal land policy was therefore influenced less by considerations of state power, and more by those of racial demographics. Frymer argues that throughout this period policymakers were united in their belief that the United States must remain a white man's nation, a conviction which he argues both drove and limited national expansion. As policymakers contemplated acquiring overseas territory, they continuously fretted that bringing large numbers of nonwhite peoples into the national fold would pollute the racial purity of American society. Such concerns delayed statehood for both New Mexico and Arizona until each had attained a majority white population, and ultimately ended various plans to acquire Cuba and portions of Mexico and Central America.

Some aspects of Building an American Empire are more convincing than others. Frymer's contention that the antebellum federal state was an institutionally underdeveloped yet tireless agent in national expansion is compelling. Yet he embraces without question the oft-repeated claim that the Civil War transformed the US nation-state into an all-powerful leviathan. New Western historians have produced a wealth of scholarship in recent years to challenge this notion; Mexican bandits, Native tribes, even ex-rebels in the South tested and exposed the shortcomings of federal power well into the late nineteenth century. For this reviewer, a more skeptical view of postbellum federal power would have created a more balanced study overall.

That said, Building an American Empire makes a persuasive case for the need to understand the relationship between US expansion, federal land policy, and state formation. This is not a comprehensive study and newcomers looking for an overview of the history of US expansion should probably start elsewhere. However, more advanced scholars, particularly those interested in the evolution of state power and westward expansion, will find much of value in this richly researched and engagingly written book.