Between roughly 1790 and 1850, America was transformed from a small agrarian society along the Atlantic coastline into a wealthy, economically diverse country that stretched across the continent to the Pacific. Eighteen new states joined the original thirteen, and the nation’s population swelled from four million to over twenty-three million. These numbers included enslaved and free Black people as well as native-born and immigrant whites. In 1850, the figure also Native Americans not living on government reservations. With increases in slavery and immigration during the early nineteenth century, the nation’s population grew more heterogeneous as it grew larger. One result was that this period of unparalleled growth and prosperity deepened divisions of class, race, gender, and nationality. The most divisive issue—whether America would be a society based on free labor or on slavery—repeatedly sparked crises that, in each case, were settled by legislative compromises. But over the course of sixty years no long-term solution was reached.

In 1790, however, the issue of slavery seemed of secondary importance to most Americans of European descent. The new nation was confidently launching an unprecedented experiment in national republican government, backed by a seemingly limitless supply of land and natural resources. Most white Americans were optimistic about the nation’s future. Even African Americans had some reason for hope as substantial numbers gained freedom and organized churches and mutual aid societies in the decade following the Revolution.

In the North, a market economy and a new system of industrial production took root. Here, revolutions in transportation, communication, and manufacturing undermined the old systems of local craft production and family farming. By the 1830s and 1840s, New England capitalists had brought workers—either women or entire families—together in the nation’s first factories to weave cloth. Other workers labored in their homes to make shoes and clothing for market. An expanding network of roads, canals, and, later, railroads carried consumer goods from the Northeast to the new settlements in Ohio, Indiana, and Illinois and brought raw materials and foodstuffs produced in the west to the east.

The South remained predominantly agricultural, but there, too, Americans felt the profound changes wrought by an international industrial revolution. Aided by the invention of the cotton gin, Southern landowners replaced tobacco with cotton as their principal cash crop and large quantities of the raw fiber fueled industrial development in England and New England. As a result, the region’s plantation economy burgeoned, spreading from the upper South to Alabama, Mississippi, Louisiana, and, by the 1840s, to Texas. As large planters increasingly dominated the South’s economy and government, they wielded kinship, religion, and racism to strengthen bonds with the majority of white southerners who owned a few enslaved persons or none at all. Yet economic differences led to growing tensions, particularly between those who lived in areas where slavery flourished and those who lived in areas where the institution was in decline. 

Tensions among white people did not, however, limit the brutality of the plantation system for African Americans. If the bonds of slavery loosened briefly in the revolutionary era, they now tightened with renewed vigor. To keep pace with the demand for cotton, the enslaved labor force expanded both numerically and geographically. For vast numbers of African Americans these changes worsened working conditions and tore families apart.

Native Americans and Mexicans also faced hardships due to white settlers' insatiable desire for land.  As they had during European colonization, many Native nations confronted either extermination or migration further westward. Some were forced out of their communities in the Southeast and onto reservations in the Indian Territory of present-day Oklahoma. Many Mexicans were also pushed out of their homes to make way for U.S. settlers in Texas and California. And in the aftermath of Texas statehood in 1845 and the Mexican American War of 1846–1848, hundreds of thousands of Mexicans came under U.S. jurisdiction.

The economic growth that drove geographic expansion also dramatically altered the lives of working Americans.  By midcentury, millions of Americans—including artisans, factory hands, domestic servants, day laborers, and even some enslaved workers—had been drawn into a market economy where they sold their labor or their products. In the process, the ideal of the self-sufficient, independent farm or artisan family was undermined as increasing numbers of women and men became dependent upon wages. At several points in this era, wage workers (by now two out of every five American workers) experienced the full impact of that dependency as manufacturing ground to a halt and tens of thousands were suddenly jobless.

Despite periodic recessions and depressions in the early nineteenth century, northern employers were more concerned about a shortage of labor than an oversupply. That concern lessened when, beginning in the 1840s, a massive wave of immigrants from northern and western Europe entered the United States, willing to work for all kinds of manufacturing and agricultural enterprises. Most of these new immigrants—many of whom came to escape economic, social, and political injustices at home—became wage laborers, contributing to the formation of a growing and distinctly multinational working class. They also intensified the effects of the Industrial Revolution: the growth of cities, a new urban culture, and transformations in family structures and gender roles. In addition, some immigrants introduced radical theories and practices, including socialism, to American politics and broadened the base of American religion.

The contributions of immigrants were not always welcomed, however. In the 1840s and 1850s, many native-born Americans blamed new immigrants for the wrenching changes that resulted from industrial and urban development.  Some joined anti-immigrant political movements; others initiated moral reform campaigns aimed at controlling the behavior of working-class immigrants; and still others physically attacked immigrants. Although free Black people were also subject to attacks by native-born white Americans, they rarely made common cause with immigrants. Instead, the two groups clashed with each other as they competed for jobs and housing.   

Industrialization, and the demographic and cultural changes that accompanied it, profoundly affected the nation’s political life. Americans engaged in intense debates over what kind of society they were creating. The commercial and industrial elite embraced a liberal capitalist interpretation of the revolutionary legacy, emphasizing the role of self-interest and the marketplace in governing social and economic relations. Many working people, especially those who did well in the new order, were attracted to the idea that liberty meant individual freedom to better themselves and improve their living standards. Others, including many of the working people dislocated by industrialization, criticized the emerging order as a betrayal of revolutionary ideals and celebrated instead republican traditions of independence, mutuality, and citizen participation derived from the French and other European revolutions as well as the American Revolution.

Working Americans—men, women, and children; free-born, enslaved, and emancipated; native-born and immigrant—resisted the dependent status that came with industrial and agricultural development. They insisted that the United States had not been created to make a few men rich and powerful at the expense of all others. They attacked the “tyranny” of their employers and masters, condemning them as “Tories in disguise,” in the words of women textile workers in the 1830s. Others argued for liberty and equality as they embraced new religious principles espoused by evangelical, Quaker, and Moravian sects. Poor white people, African Americans, and women were especially keen to claim their spiritual equality, and to translate it into practical demands for divinely sanctioned rights whenever they could. Working people defended their interests in a variety of other ways as well, through local workingmen’s parties, trade unions, cooperative workshops, utopian communities, strikes (engaged in by free and enslaved workers), and outright rebellion, most notably among enslaved persons. Some working women demanded rights for their sex, as did their middle-class counterparts. Growing numbers of women and men also denounced alcohol and prostitution and demanded the abolition of slavery.

Of all the diverse claims for social justice raised in these years, one—the end of slavery—became the central political issue of the day. Over the decades, the country divided between Americans who desired a nation of free labor, as in the North, and Americans who believed that only a system based on enslaved labor, as in the South, could guarantee social order. A basic question, one that shaped American politics, moral values, and the economy, thus emerged as the United States expanded westward and new territories sought statehood: should these new states rely on free or enslaved labor? Several political compromises from 1820 onward maintained an uneasy peace between the two systems. By 1850, however, the acquisition of new territories as a result of the U.S. war with Mexico intensified debates and steered the young nation toward civil war.