In the tumultuous atmosphere of the decades leading up to the Civil War, the combined effects of religious millennialism, technological revolutions, and the growth of a capitalist economy led numerous Americans to propose radical schemes for transforming their society. At least a hundred cooperative colonies were founded in the 1830s to 50s, leading Ralph Waldo Emerson to famously observe that it seemed every "reading man" had a "draft of a new community in his waistcoat pocket." This dissertation explores a unique strain of mid-nineteenth-century utopianism that featured geometrically distinct architectural and urban plans. These schemes include a square land reform grid and radial republican village proposed by the National Reform Association, phrenologist Orson Fowler's octagon house, Henry Clubb's anti-slavery vegetarian Octagon Settlement Company, a hexagonal city published by the anarchist Josiah Warren, and an ovoid house and circular institution of Equitable Commerce proposed by the Spiritualist John Murray Spear and his followers.

I also analyze Thomas Jefferson's octagonal houses and square land grids as precedents for the nineteenth-century utopian projects. The creators of these plans were motivated to embrace geometric forms in part because of an emerging functionalist view that regarded the built environment as capable of not just representing but also directly shaping bodies and minds. At the same time that the geometric utopians spoke a language of functional effects, however, they also, consciously and unconsciously, used their plans as aesthetic and rhetorical devices to convince and inspire potential converts. Social reformers employed geometric diagrams to convey an affect of transparency at a time when many antebellum Americans saw the levers of political and economic power as increasingly mediated and remote. By exploring the links between utopians' ideas about architecture and causes such as phrenology, Spiritualism, anarchism, land reform, abolitionism, vegetarianism, and spelling and writing reform, I construct a deeper context for these geometric utopian projects that recovers some of their radical, imaginative, and critical spark, while shedding new interpretive light on the visual culture of mid-nineteenth-century radical reform movements.