This paper utilizes raciolinguistic genealogy (Flores, in International Journal of the Sociology of Language 2021:111-115, 2021) to explore an historical case study of Spanish Franciscan missionaries in Alta California during an early period of colonization spanning the seventeenth-nineteenth centuries. In the study, I apply a raciolinguistic lens to investigate the racialized and racist basis for a language ideology of contempt (Dorian, in: Small-Language Fates and Prospects (pp. 264-283). Brill). Imported from Europe, this ideology devalued both Indigenous languages and Peoples, acting as a filter for language policymaking at multiple levels of the Spanish Empire and the mission institution. Guided by this ideology, Franciscan missionaries strategically implemented both monolingual and multilingual pedagogies for forced assimilatory religious schooling, which was intended to contribute to a project of linguicide among local Indigenous Peoples in the region. This structural "killing of languages without the killing of speakers" (Bear Nicholas in Briarpatch 40:5-8, 2011: 4) would contribute to Spanish settler colonization in New Spain and Alta California, which sought to dominate Indigenous Peoples and extract their labor power through "elimination via absorption" (Wolfe, in: Traces of history: Elementary structures of race, Verso Books, 2016). The concept of "genocidal multilingualism" is offered to interpret the missionaries' strategy to learn and expropriate the languages of local Indigenous communities for the purposes of linguicide and forced assimilation. Today, multilingualism is often affiliated with political support for linguistic and cultural diversity and challenges to hegemonic monolingualism (Kubota in Applied Linguistics 37:474-494, 2016). However, the current neoliberal political context in California and the U.S. may be similarly influenced by a raciolinguistic ideology of contempt that devalues minoritized languages and users, including Indigenous Peoples and their languages, reproducing the linguicidal language shift that characterizes the historical legacy of colonization in the United States.