In this unique reference, leading historians describe not only how the expansion of the American nation in the early 19th century was a turning point in U.S. history that led to the Civil War, but also alternative scenarioswhat happened and what almost happened.This volume poses what if questions about ten crucial tipping points in the history of U.S. expansionism between 1800 and the Civil War. It not only describes what happenedin the case of Lewis and Clark, the War of 1812, the Monroe Doctrine, railroads and telegraphs, the Mexican War, the gold rush, the Compromise of 1850it also offers alternative scenarios, essays on what could have happened.In this exciting and imaginative approach to history, students not only develop analytical skills by tracing the causes and effects of crucial events; they are empowered by the knowledge that at moments when history hangs in the balance, many paths are possible, and that they, as citizens, can tip the scale.