Hypertension and high-normal blood pressure (BP) increase the risk for cardiovascular diseases. Examining trends in hypertension and high-normal BP among US adults is crucial. Participants aged 20 years or older from the 1999-2018 National Health and Nutrition Examination Surveys, were included. Trend analyses were performed to assess temporal changes in prevalence of hypertension and high-normal BP among US adults. Among the 48,580 participants included in this analysis, the mean (SD) age was 47.2 years (18 years) and 50.9% were women. Age-adjusted prevalence of hypertension was stable from 1999 to 2000 (29.5% [95% CI 26.6-32.3%]) through 2017-2018 (31.9%, [95% CI 29.0-34.7%]) (P = 0.265 for linear trend). Age-adjusted prevalence of high-normal BP decreased from 10.9% (95% CI 9.4-12.5%) in 1999-2000 to 8.0% (95% CI 7.1-9.0%) in 2007-2008, then increased to 9.8% (95% CI 8.3-11.3%) in 2017-2018 (P = 0.002 for nonlinear trend). Compared with men, hypertension and high-normal BP was less likely among women (multivariable-adjusted prevalence ratio, 0.90 [95% CI 0.84-0.97]; 0.68 [95% CI 0.52-0.88], respectively). Compared with non-Hispanic Black, high-normal BP was less likely among Mexican American, non-Hispanic White, and other race (multivariable-adjusted prevalence ratio, 0.59 [95% CI 0.44-0.79]; 0.53 [95% CI 0.41-0.69]; 0.56 [95% CI 0.74 - 0.71], respectively). The same held for hypertension.