The United States did not always stretch from the Atlantic to the Pacific. For well over a century, the first immigrants who came to North America settled along the Atlantic coast. The natural barrier of the Appalachian Mountains kept these early colonial settlements from expanding. But there were always some explorers, hunters, and traders who ventured into unknown regions. They brought back stories of the wonders of the lands to the west. As the East Coast became more densely populated, game became scarcer and crops began to fail as the soil lost its fertility. People needed more room, and Kentucky became the next great destination for expansion. John Filson, the author of the Adventures of Colonel Daniel Boone, wrote that Kentucky flowed "with milk and honey . . . a land of wheat and barley, and all kinds of fruits. You shall eat bread without scarceness, and not...