Background: African Americans are at higher risk for preeclampsia compared with Caucasians, but longitudinal changes are unknown. We hypothesized that preeclampsia rates among African Americans would be higher than that of Caucasians and over time would maintain a consistent divergence. Methods: We analyzed the annual prevalence rates and calculated prevalence odds ratios (POR) with 95% confidence intervals (95% CI) for preeclampsia comparing 4,644 African American (weighted 608,109) with 12,131 Caucasian (weighted 1,844,391) women from the National Hospital Discharge Survey (1979-2006), including all women for whom a delivery was associated with preeclampsia. We estimated the race-specific prevalence of preeclampsia while adjusting for age, geographic region, diabetes, essential hypertension, prior myocardial infarction, heart failure, benign essential hypertension complicating a pregnancy, transient hypertension, and gestational diabetes. Results: There was an increasing trend in preeclampsia rates per year from 1979 to 2006 for African Americans [POR 0.76 (95% CI 0.49, 1.03)] and Caucasians [0.29 (95% CI 0.17, 0.41)]. However, there was an initial decrease in prevalence from 1979-1988 among African-Americans [-0.96 (95% CI -1.78, -0.14)] that was not seen in Caucasians [0.12 (95% CI -0.33, 0.57)]. Across all study years, preeclampsia rates remained higher for African Americans compared to Caucasians, from a POR of 0.98 (95% CI 0.96, 1.0) to POR of 1.75 (95% CI 1.73, 1.78). Conclusion: There was an increase in the prevalence of preeclampsia in African Americans compared to Caucasians in the most recent decade under study. This may be explained by healthcare system changes and disparities in obesity. Action is needed to reduce the trajectory of future cardiovascular disease caused by preeclampsia.