In April 1780, John Jay became the first accredited minister of the United States to set foot in Madrid. He had three assignments from Congress: to persuade his majesty, Carlos III, to 1) accede to the Franco-American alliance, 2) sign a treaty of commerce with the United States, and 3) grant the Americans a financial subsidy or loan. Jay achieved none of those objectives. He left Spain two years later, in May 1782, without treaty or agreement of any kind—and it is likely for this reason that scholars have shown little interest in his work. Yet the records of his negotiations, I will argue, are significant for the insight that they offer into the nature of diplomatic law in the revolutionary era. 1