The Los Angeles County Demographic Data Project preserves and makes accessible a dataset tracing social changes in the City of Los Angeles, L.A. County, and 86 municipalities between 1950 and 2010. The Los Angeles County demographic dataset includes over 90 discrete data files and represents the culmination of more than a decade of work by historian Becky Nicolaides and her team while completing research for her book The New Suburbia: How Diversity Remade Suburban Life in Los Angeles After 1945 (Oxford, 2024). Nicolaides’ research for The New Suburbia was supported by grants from NEH, the American Council of Learned Societies the John Randolph Haynes & Dora Haynes Foundation, and other organizations. The dataset traces many facets of demographic change in Los Angeles and 86 nearby municipalities along with poverty rates and voter registration data. Nicolaides and her team painstakingly collected data for each municipality for 54 variables relating to race and ethnicity, country of origin, class, occupation, education, age, family status, and housing from the U.S. Census and voter registration data from the California Secretary of State. Nicolaides and her team carefully documented their methodology and accounted for many changes in definitions used by the U.S. Census. The resulting dataset allows for meaningful, granular comparisons among municipal data for seven decennial years (1950, 1960, 1970, 1980, 1990, 2000, and 2010).