Abstract Body: Diet quality is a key modifiable risk factor for cardiovascular health. Racial and ethnic disparities in diet quality have been well-documented. However, few studies test how geographical context affects these associations in older women. Furthermore, these inequities have been reported to be unevenly distributed across different geographic regions in the United States (US). This analysis aimed to examine differences in diet quality across the four US Census 2020 regions (i.e., Northeast, Midwest, South, West) using data from the Women's Health Initiative (WHI) study. Informed by prior studies, we hypothesized that diet quality would differ across the four US Census regions, with the Northeast having the highest diet quality and the South having the lowest diet quality. In a secondary analysis of baseline data from the WHI, a large-scale longitudinal study of postmenopausal women, participants' dietary intake was assessed using a food frequency questionnaire. A Healthy Eating Index (HEI-2020) score was calculated as a measure of overall diet quality. Linear regression models were used to compare HEI-2020 scores across the four US Census regions adjusting for relevant sociodemographic covariates (age, education, income, employment, marital status, and race and ethnicity). In 161,299 women (M_age= 63.2 ±7.2) with dietary intake data, mean HEI-2015 scores differed across regions, with the highest score in the West (63.7 ±0.1) and the lowest score in the Northeast (62.1 ±0.1). These regional differences persisted even after adjusting for sociodemographic covariates (p<0.001). Statistically significant interactions between race/ethnicity and census region on HEI-2020 total score were observed. Non-Hispanic White women living in the West region had the highest diet quality (64.9 ±0.2), while Hispanic women of any race in the Northeast had the lowest diet quality (61.1 ±0.1). This analysis reveals significant regional differences in diet quality among postmenopausal women across the US. Contrary to our hypothesis, WHI participants in the West region exhibited the healthiest diets and women in the Northeast region exhibited the least healthy diets. Findings highlight a need for targeted dietary assessments and public health initiatives to assess for regional differences in dietary intake. Given the disparities in diet observed in this analysis, other population-wide cohort studies should further account for potential geographic differences involving diet analyses.