Countless studies have examined Congress's capacity to enact laws. I explore the opposite: efforts to repeal laws. Repeals fit the grant's themes because they represent some of the most consequential policy disagreements in history. Repeals also provide a novel substantive and methodological approach to testing theories of Congress's institutional performance. Yet repeals have been almost entirely overlooked by scholars. I am seeking the SSRC's support to write a book on repeals from 1877 to 2012. Given its historical scope and core theories, I believe the book will be of interest to a wide range of scholars.