Much of What Hath God Wrought revolves around the political and social challenges of territorial expansion in the United States during the period between 1815 and 1848. This era, marked by rapid growth and change, saw the United States grappling with the implications of its expanding borders, not only in terms of geography but also in the realm of its national identity, politics, and the fabric of its society. The theme of territorial expansion is explored through multiple lenses, highlighting the complexity of incorporating vast lands and diverse peoples into the young nation.

Howe examines how a mix of Manifest Destiny, economic interests, and the desire for national security drove expansion, yet it also brought to the forefront the nation’s internal contradictions, especially regarding freedom, democracy, and the treatment of Indigenous and other marginalized groups. American expansion often entailed the forcible displacement and suffering of Indigenous tribes. Howe asserts:

‘Manifest destiny’ served as both a label and a justification for policies that might otherwise have simply been called American expansionism or imperialism. The assumption of white supremacy permeated these policies. It never occurred to U.S. policymakers to take seriously the claims of nonwhite or racially mixed societies to territorial integrity (725).