Between May 21 and June 16, 1791, Thomas Jefferson and James Madison went on a trip together through Upstate New York and parts of New England on horseback. Whether the country could overcome regional and political differences and remain unified, however, was still very much in question. Hence why some observers at the time wondered whether this excursion into Federalist New England by the two most prominent southern Democratic-Republicans, both future presidents, had an ulterior motive.

While in Vermont, they focused on the sugar maple tree, which many hoped might offer a domestic alternative to slave-grown sugar cane imports. An encounter with a free Black farmer at Fort George resulted in a journal entry that illuminates their attitudes toward slavery and race. A meeting with members of the Unkechaug tribe on Long Island led to a vocabulary project that preoccupied Jefferson for decades, and which remains relevant today.

Madison later recalled that the trip made Jefferson and him "immediate companions," solidifying a bond with almost no peer in the annals of American history, one that thrived for fifty years. Jefferson declared at the end of his life, that his friendship with Madison had been "a source of constant happiness" to him. This book reveals the moment when it took hold.