Since 1791, the federal Constitution has been amended only 17 times, while the 146 state constitutions have been amended 5,900 times. What explains the federal Constitution’s stability relative to the states? My book manuscript argues that ongoing state constitutional revision resolves national constitutional controversies, preempting amendments to the federal Constitution, and quieting conflict between the branches of the federal government. I defend the claim with an original dataset of all 331 proposed state constitutions from 1776-2018 and a series of chronological case studies of state constitutional revision, backed by archival research. Finally, I argue that frequent, popular revision grants the state constitutions a democratic legitimacy that the national Constitution lacks.