Roman Catholic sisters first traveled to the American West as providers of social services, education, and medical assistance. In Across God's Frontiers, Anne M. Butler traces the ways in which sisters challenged and reconfigured contemporary ideas about women, work, religion, and the West; moreover, she demonstrates how religious life became a vehicle for increasing women's agency and power. Moving to the West introduced significant changes for these women, including public employment and thoroughly unconventional monastic lives. As nuns and sisters adjusted to new circumstances and immersed themselves in rugged environments, Butler argues, the West shaped them; and through their labors and charities, the sisters in turn shaped the West. These female religious pioneers built institutions, brokered relationships between Indigenous peoples and encroaching settlers, and undertook varied occupations, often without organized funding or direct support from the church hierarchy. A comprehensive history of Roman Catholic nuns and sisters in the American West, Across God's Frontiers reveals Catholic sisters as dynamic and creative architects of civic and religious institutions in western communities.