Volume 4 of The Selected Papers of John Jay opens in January 1785 as John Jay assumes office as secretary for foreign affairs and brings system and order to the long-neglected Department of Foreign Affairs. It explores Jay's administration of all aspects of American foreign affairs, including his efforts to implement the peace treaty with Great Britain, facilitate American trade, and renegotiate an intrusive consular treaty with France. It examines Jay's divisive negotiations with Diego de Gardoqui and his politically embarrassing dispute with Lewis Littlepage. It depicts his antislavery efforts as president of the New-York Manumission Society and his participation in the Americanization of the Episcopal Church. It documents his promotion of constitutional change as the weaknesses of the Confederation thwart diplomacy and his defense of the proposed new Constitution as an author of The Federalist and of a far more influential pamphlet. The volume closes as Jay takes leave of absence from office to support ratification of the Constitution as delegate to the New York Ratifying Convention. Access to people, places, and events in the volume is facilitated by detailed annotation, illustrations, a biographical directory, and a comprehensive index. The publication of this volume has been supported by a grant from the Gilder Lehrman Institute of American History.