By 1815, peace had come to the United States. American and British officials signed the Treaty of Ghent on December 24, 1814, to end the War of 1812 (1812–15). The treaty halted hostilities and restored U.S. boundaries that existed before the war. Just as important, British troops defeated the army of French emperor Napoléon Bonaparte (1769–1821) in June 1815 at the Battle of Waterloo in Belgium. Europe at last rested from war and stopped stirring up trouble for America on the high seas. A difficult time in America's early history had come to an end.

Nationalism, a spirit of national unity and loyalty, took hold of Americans. No longer did they think in terms of one state dominating over another. Instead, they thought of the states as bound together in a truly united nation. The war not only shaped America's self-image but taught the young nation the following powerful lessons: The U.S...