The United States government, represented by the Office of the Solicitor General, appears before the Supreme Court more than any other litigant. The Office’s link to the president, the arguments it makes before the Court and its ability to alter the legal and policy landscape make it the most important Supreme Court litigant bar none. As such, scholars must understand the Office’s role in Supreme Court decision making and its ability to influence the Court. It examines whether and how the Office of the Solicitor General influences the United States Supreme Court. Combining archival data with recent innovations in the areas of matching and causal inference, the book finds that the Solicitor General influences every aspect of the Court’s decision-making process. From granting review to cases, selecting winning parties, writing opinions and interpreting precedent, the Solicitor General’s office influences the Court to behave in ways it otherwise would not.