Chronic ingestion of excess sodium has been associated with high blood pressure, heart disease, and stroke. Limited research has suggested a relationship between increased sodium intake and the development of preeclampsia. This study investigated the association between elevated sodium in drinking water with preeclampsia using a hospital-based case-control study of 10,114 pregnant women in Iowa in the United States. Health records of women who delivered at the University of Iowa Hospitals and Clinics in Iowa City, Iowa, USA, between May 2009 and August 2020 were obtained from the Intergenerational Health Knowledgebase. Water quality data for community water systems from Safe Drinking Water Act compliance reporting and Consumer Confidence Reports (CCR) were used to estimate maternal exposure to sodium in drinking water. Logistic regression models were calculated to estimate the odds of preeclampsia based on median sodium concentrations reported by public water systems from 2000 to 2019. Preeclampsia was associated with a 38% increased odds (adjusted odds ratio (aOR) 1.38, 95% confidence interval (CI) 1.13-1.69) when women were exposed to concentrations between 20-69 milligrams per liter (mg/L), above EPA's recommendation for individuals on a very low sodium diet. Increased odds of 5% and 16% were also found at concentrations between 70-102 mg/L and greater than 256 mg/L but were not statistically significant. The lower odds at higher sodium concentrations may be due to consumers using alternative drinking water sources due to taste issues that are noted to arise between 30-60 mg/L. Preeclampsia diagnosis was strongly associated with gestational age, parity, newborn count, and body mass index. Better data on individual exposure through drinking water is needed to account for factors like home softeners, which can greatly increase sodium levels at the tap, or those users seeking out alternative water supplies (like bottled water) due to taste issues arising from greater salinity.