A Princely Domain.

On paper, the United States was an extremely large country at the close of the Revolutionary War. In the Treaty of Paris, which ended the war in 1783, the British ceded to the new nation all the territory between the Atlantic Ocean and the Mississippi River, except New Orleans and Spanish Florida. When George Washington took the oath of office as the nation's first president five years later, he became the leader of a country that stretched for more than a thousand miles in every direction—an impressive domain by any standard. However, with the exception of outposts along navigable inland rivers, most Americans lived along a tiny ribbon of settlement on the Atlantic seaboard at the close of the eighteenth century. The grand new maps rolling off American printing presses contained another fiction as well: they failed to account for the fact that tens of...