Introduction

In the 60 years from 1800 to the opening of the Civil War, the American nation expanded, matured, and divided. Expansion came first. It began in 1803 with Thomas Jefferson’s purchase of the Louisiana Territory, and in 1819 the United States acquired the rest of Florida by treaty. Then, in the decade of the 1840s, with stunning suddenness amidst a burst of expansionist sentiment, the country extended its boundaries westward. The nation first annexed Texas (1845) as the 31st state, gained the Oregon Country by treaty (1846), and, after a war, seized the northern third of Mexico (1848), which would become the states of California, New Mexico, and Arizona. The Gadsden Purchase of 1854 would complete this expansion. At the conclusion of this growth, the United States had become a continental nation, stretching from the Atlantic to the Pacific.

At the same time that the United States expanded, and in part because of it, the civil contract of the nation and its political unity began to unravel. The issue of African slavery became the dominant theme of American political life. Opposition to the “peculiar institution” grew as the country expanded to the West. And the abolitionist movement, as it would be called, was only one of many reform movements that engaged the energies of men and women. Among the more important of these were women’s rights and the temperance movement. These issues would continue to engage the nation through the Civil War and well into the 20th century.

—Malcolm J. Rohrbough