This study assessed the temporal relationship of elevated blood pressure (BP) with left ventricular hypertrophy (LVH) and geometric changes in a longitudinal cohort of adults. Left ventricular mass index (LVMI), relative wall thickness (RWT), and BP were measured at 2 time points 4.1 to 14.9 years apart between 2000 and 2016 among 984 adults (677 White and 307 Black people; 41.1% men; age range, 24.2–56.7 years) in the Bogalusa Heart Study cohort. Cross-lagged path analysis models were used to examine the temporal relationship of BP with LVMI and RWT in subjects who did not take antihypertensive medications (n=693). The cross-lagged path coefficients did not differ significantly between race and sex groups. In the combined sample, the path coefficients from baseline systolic BP to follow-up LVMI/RWT were significantly greater than the path coefficients from baseline LVMI/RWT to follow-up systolic BP (0.111 versus −0.005 for LVMI, P=0.010 for difference; 0.146 versus 0.004 for RWT, P=0.002 for difference). Hypertensive subjects at baseline had a significantly higher incidence rate of concentric LVH at follow-up compared with normotensive subjects (19.4% versus 9.7%, P<0.001 for difference), but incident eccentric LVH did not show such a difference between hypertensive and normotensive subjects (5.4% versus 4.4%, P=0.503 for difference). Diastolic BP showed similar results to those of systolic BP. In conclusion, the findings on these one-directional paths provide strong and fresh evidence that elevated BP precedes the development of LVH, especially concentric LVH, during the young-to-midlife adult age period.