WIC can improve maternal and childhood health and nutrition, yet only 50% of people who qualify for WIC receive benefits, with racial disparities across states. Beyond state and national estimates, less is known about zip code-level racial/ethnic coverage rates or the factors influencing program reach. This study will be the first large-scale assessment of overall and racial/ethnic coverage rates in WIC by zip code. This study has two aims: (1) to quantify 2022 racial/ethnic WIC coverage rates by zip code in 14 states across the United States, and assess environmental influences on zip code level racial/ethnic coverage rates; and (2) to understand organizational influences on racial/ethnic coverage rates via 24 Key Informant Interviews with WIC leaders. This mixed methods study builds on previous research, relationships with USDA FNS experts, and robust preexisting partnerships with WIC agencies in the USDA/Tufts THIS-WIC study.