That the places we live, work, and play matter for individual and population health across the human life course is both incredibly consequential and relatively uncontested in modern social epidemiology. In a keynote address at the 2019 GEOMED meeting, Ana Diez Roux-an early proponent of applying the sociological neighborhood effects framework to the descriptive and explanatory tasks of epidemiology-summarized four evolving stages of conceptual thinking in the place and population health scholarship since the 1990s1: (1) places are context for health, (2) places are causes ofhealth, (3) places are effect modifiers or reinforcers of individual or social health-relevant processes, and (4) places are components of complex systems that dynamically produce and distribute experiences, exposures, and opportunities, which give rise to socially structured patterns of population health.This progression toward increasingly complex and dynamic thinking about relations between places and population health is evident in the growth and evolution of research examining how residential locale affects reproductive and perinatal health outcomes. In this issue of AJPH, Krieger et al. (p. 1046) make an important contribution to this body of research by asking whether the historical process of mortgage redlining in specific New York City neighborhoods predicts the risk for preterm birth among women residing in those neighborhoods and delivering liveborn, singleton infants in 2013 through 2017. By contrast to much of the neighborhood effects research focusing on temporally proximate or contemporary exposures and outcomes, Krieger et al. use the 1938 maps created by the federally sponsored Home Owners Loan Corporation (HOLC) of investment "risk" guiding mortgage lenders as predictive exposures. These maps-where "hazardous" neighborhoods are outlined in red giving rise to the term "redlining"-codified the racialized government policy of public investment in White and middle-class communities and disinvestment in neighborhoods with Black, Puerto Rican, or foreign-born residents. Anyone doubting the explicit racialized motivation underpinning the map categories should peruse the comments and notes abstracted from the original maps as summarized in Table B of Krieger et al. (available as a supplement to the online version of their article at http://www.ajph.org).The inclusion of 1938 mortgage lending policy is not evoked in this study as a direct experience or exposure for women who are not giving birth until the second decade of the 21st century. Instead, Krieger et al. posit that this historical fact (the HOLC maps and their role in guiding mortgage lending) stands as an influential node in the spatiotemporally dynamic urban ecology of populations and places. The authors find modest empirical evidence that the 1938 HOLC categories predicted contemporary risk for preterm birth, independent of important individual demographic, socioeconomic, and health risk factors. These findings have implications for how we interpret cross-sectional analysis of geographic variation in health, how we conceive of the social causes of health and health disparities, and consequently what kinds of public health actions might plausibly disrupt the status quo ofhealth inequity.