“Fiesta Immemorial” is a social history of capitalist development in Southern California that excavates the constitutive relations between American settlers and Cahuilla, Cupeño, Serrano, Luiseño, and Kumeyaay peoples during the first half of the 20th century. Addressing the absence of Native politics in histories of US capitalism, it shows how US federal Indian agents, law enforcement, entrepreneurs, boosters, philanthropists, reformers, and residents collaborated to constrain California Native nations’ sovereign practices across sites of labor, leisure, and livelihood in order to naturalize American juridical rule, enforce capitalist market relations, and secure the settler social order. Drawing on booster literature, businessmen’s journals, letters, and memoirs, the ephemera of missionaries and reformers, Bureau of Indian Affairs agents and government officials’ correspondence, Congressional reports, arrest records, hobby ethnographies, and historical newspapers, “Fiesta Immemorial” explores how seemingly mundane sites, such as agricultural fairs, philanthropic programs, New Deal-era works projects, backcountry tourism, and real estate ventures were crucial nodes of conflict. It argues that a specifically colonial apparatus of suspecting, policing, and jailing Native people and the non-Natives who socialized with them accompanied these assimilatory aspirations. At the same time, cultural and knowledge producers enamored with the region circulated narratives that confirmed the apparent inevitability of the capitalist market and the American state’s success, even as these carceral and regulatory campaigns continually failed. Paying particular attention to archival absences, competing notions of time, and ubiquitous surveillance, “Fiesta Immemorial” illustrates the central role of Southern California Indian nations and people in the region’s development, beginning with its turn-of-the-century “picturesque” pastoral land speculation and ending at the post-World War II defense industry boom.