William C. C. Claiborne, the first governor of Orleans Territory, was at the hub of officials who grappled with the political, diplomatic, and administrative challenges that arose following the Louisiana Purchase in 1803. Letters both to and from Claiborne during the critical months of 1804–1805, mysteriously excluded in 1917 from Dunbar Rowland’s Official Letter Books of W. C. C. Claiborne, 1801–1816, are now made widely accessible, over half of them published here for the first time. To enhance appreciation of the letters, Jared William Bradley has furnished biographical sketches of thirty-one heretofore little-known individuals crucial to Claiborne’s correspondence, delineating their personalities and their contributions to the development of law and the establishment of American government in the French Creole society. Bradley also treats in four essays the origins and growth of the “Municipal,” or the New Orleans city council; two organizations of businessmen that were ensnared in the so-called Burr Conspiracy in 1807; and the early history of Fort St. Philip, which guarded access to New Orleans from the Gulf of Mexico. Bradley’s essays joined with 218 of Claiborne’s letters makes Interim Appointment of incalculable value. It provides fresh insights into the political, constitutional, and social histories of Louisiana and the United States.