This Article offers the first systematic attempt to measure the development of shareholder protection in the United States across time. Using three indices developed to measure the relative strength of shareholder protection across nations, we evaluate numerically the protections corporate and securities law have offered shareholders from the beginning of the twentieth century to the present day. We do so by tracking the rights accorded to shareholders across time under three important sources of corporate law, Delaware and Illinois and the Model Business Corporation Act.Our novel study yields novel results. First, we find that the protections afforded to shareholders by state corporation law have decreased since 1900 but only modestly so. This implies that, contrary to the assumptions of many scholars, state competition in corporate law has not significantly eroded shareholder rights. Second, when we add in measures that count protections provided by federal as well as state law, we find that shareholder protection improved across time. This implies that federal intervention has played a crucial and perhaps underappreciated role in shaping U.S. corporate law. Beyond its specific findings, this study illustrates how empirical analysis of legal trends provides scholars with a new means for analyzing and resolving fundamental questions in corporate law.