Summary This infrastructure proposal aims to further advance capabilities in the social sciences (broadly defined) to collect data on the daily lives of U.S. families and individuals. These data will be more accurate, more granular, and more comprehensive than is currently possible in traditional survey-based research. The context for this is the Understanding America Study (UAS), the probability-based Internet panel we have been building at USC since 2014. The infrastructure includes the combination of many data types (including survey data, information from wearables, contextual and administrative linkages, ecological momentary assessments, self-recorded narratives, and electronic records of financial transactions), as well as an open communication with the wider research community both in data dissemination and in soliciting input on content and methods. The UAS currently comprises about 10,000 U.S. residents (including a 2,500 person California oversample), recruited by address-based sampling and provided with Internet-enabled tablets if needed. Surveys are conducted in English and Spanish. We propose to expand the UAS national sample to 20,000 respondents, with subsamples of Blacks, Asians, and Hispanics of at least 3,000 each. The information collected will focus on factors explaining racial and socio-economic disparities over the life course, including racial discrimination, inequalities in access to education and healthcare, differences in the physical and social environment, and, more generally, the various opportunities and obstacles one encounters over the life course. The proposed project team covers a broad spectrum of substantive expertise on disparities, racial discrimination, environmental health, child development, health, and cognition over the life course, as well as aging and retirement, consumption, work, and income. To encourage input from the research community, we envision a program of added survey modules on inequality-related topics proposed by outside researchers, as well as an annual research conference. The basic premise underlying the project is that the only feasible approach to comprehensively investigating the impact of differences in the life course on observed inequality is to enact a robust multi-method approach that provides the means of accounting for as many explanatory factors as possible. Within that context, naturally occurring experiments can be exploited to help identify causal pathways of interest (e.g., when air quality in a neighborhood improves due to a plant closure; a policy change that affects the quality of schools in a certain area). Thus, our proposed project aims to create and make available to the research community a uniquely detailed and focused collection of information on U.S. households and individuals. To achieve this goal, we aim to strategically integrate selected external data sources with UAS survey data and expand the already broad set of topics covered by UAS surveys.