In the decades following the Civil War, America was transformed from a rural republic to an urban state. Frontiers vanished in the face of westward expansion. Floods of immigrants streamed through the great eastern seaports, fueling the need for industrial labor. And transcontinental railroad lines linked the country together like never before. The film explores the people behind the changes, the birth of organized labor, The Homestead Act of 1862, and the birth of the environmental movement.