In examining how the United States gained control over the northern borderlands of Spanish America, this work reassesses the diplomacy of President James Madison. Historians have assumed Madison’s motive in sending agents into the Spanish borderlands between 1810 and 1813 was to subvert Spanish rule, but J. C. A. Stagg argues that his real intent was to find peaceful and legal resolutions to long-standing disputes over the boundaries of Louisiana at a time when the Spanish-American empire was in the process of dissolution. Drawing on an array of American, British, French, and Spanish sources, the author describes how a myriad cast of local leaders, officials, and other small players affected the borderlands diplomacy between the United States and Spain, and he casts new light on Madison’s contribution to early American expansionism.