Policy choices sometimes appear stubbornly persistent, even when they become politically unpopular or economically damaging. This paper offers the first systematic empirical investigation of how persistent policy choices are, defined as whether an electorate’s or legislature’s decisions affect whether a policy is in place decades later. I create a new dataset that tracks the historical record of more than 800 policies that were the subjects of close U.S. state referendums since 1900. In a regression discontinuity design, I estimate that passing a referendum increases the chance a corresponding policy is operative 20, 40, or even 100 years later by over 40 percentage points. I collect additional data on U.S. Congressional legislation and international referendums and use existing data on state legislation to document similar policy persistence for a range of institutional environments, cultures, and topics. I develop a theoretical model to distinguish between possible causes of persistence, and I present evidence that persistence arises because policies' salience systematically declines over time. Calibrating my model suggests that many policies remain in place—or not—regardless of popular support.