Introduction: The optimum physical activity dose to achieve during young adulthood to prevent hypertension using the 2017 American College of Cardiology/American Heart Association guidelines remains undefined. This study aims to determine the association between level and change in physical activity through the adult life course and the onset of hypertension using these 2017 definitions. Methods: In 2020, prospective community-based cohort data of 5,115 Coronary Artery Risk Development in Young Adults study participants were analyzed. The cohort included Black and White men and women aged 18–30 years at baseline (1985–1986) at 4 urban sites, collected through 30 years of follow-up (2015–2016). Individualized physical activity trajectories were developed for each participant using linear mixed models. Results: Black women reported the lowest physical activity levels from young adulthood through middle age. Lower physical activity score (per 100 units) at age 18 years was associated with 4% (95% CI=1%, 7%, p=0.002) higher odds of hypertension incidence. Each additional 1-unit reduction per year in physical activity score was associated with 2% (95% CI=1%, 3%, p=0.001) higher annual odds of hypertension incidence. Meeting approximately the current minimum physical activity guideline levels at age 18 years and through follow-up was not protective of hypertension incidence; however, meeting approximately twice the current minimum physical activity guideline level at age 18 years and through follow-up was protective of hypertension incidence. Conclusions: Moderate physical activity levels may need to exceed current minimum guidelines to prevent hypertension onset using 2017 American College of Cardiology/American Heart Association definitions.