The American Constitution, ratified in 1789, committed the United States to two of the major forces of the first half of the nineteenth century, liberalism and nationalism. Initially, this constitutional commitment to national unity was challenged by divisions over the power of the federal government vis-a-vis the individual states. Bitter conflict erupted between the Federalists and the Republicans. Led by Alexander Hamilton (1757-1804), the Federalists favored a financial program that would establish a strong central government. The Republicans, guided by Thomas Jefferson (1743-1826) and James Madison (1751-1836), feared centralization and its consequences for popular liberties. These divisions were intensified by European rivalries because the Federalists were pro-British and the Republicans pro-French. The successful conclusion of the War of 1812 against the British brought an end to the Federalists, who had opposed the war, while the surge of national feeling generated by the war served to heal the nation's divisions.

Another strong force for national unity came from the Supreme Court while John Marshall (1755-1835) was Chief Justice from 1801 to 1835. Marshall made the Supreme Court into an important national institution by asserting the right of the Court to overrule an act of Congress if the Court found it to be in violation of the Constitution. Under Marshall, the Supreme Court contributed further to establishing the supremacy of the national government by curbing the actions of state courts and legislatures.

The election of Andrew Jackson (1767-1845) as president in 1828 opened a new era in American politics. Jack-sonian democracy introduced a mass democratic politics. The electorate was expanded by dropping traditional property qualifications; by the 1830s, suffrage had been extended to almost all adult white males.

By the mid-nineteenth century, American national unity was increasingly threatened by the issue of slavery. Like the North, the South had grown dramatically in population during the first half of the nineteenth century. But its development was quite different. Its cotton economy and social structure were based on the exploitation of enslaved black Africans and their descendants. The importance of cotton is evident from production figures. In 1810, the South produced a raw cotton crop of 178, 000 bales worth $10 million. By 1860, it was generating 4.5 million bales of cotton with a value of $249 million. Ninety-three percent of southern cotton in 1850 was produced by a slave population that had grown dramatically in fifty years. Although new slave imports had been barred in 1808, there were four million African-American slaves in the South by 1860, four times the number in 1800. The cotton economy and plantation-based slavery were intimately related, and the attempt to maintain them in the first half of the nineteenth century led the South to become increasingly defensive, monolithic, and isolated. At the same time, the growth of an abolitionist movement in the North challenged the southern order and created an "emotional chain reaction" that led to civil war.

As polarization over the issue of slavery intensified, compromise became less feasible. When Abraham Lincoln, the man who had said in a speech in Illinois in 1858 that "this government cannot endure permanently half slave and half free," was elected president in November 1860, the die was cast. Lincoln carried only 2 of the 1, 109 counties in the South; the Republicans were not even on the ballot in ten southern states. On December 20, 1860, a South Carolina convention voted to repeal ratification of the Constitution of the United States. In February 1861, six more southern states did the same, and a rival nation—the Confederate States of America—was formed. In March, fighting erupted between North and South.

The American Civil War (1861-1865) was an extraordinarily bloody struggle. More than 600, 000 soldiers died, either in battle or from deadly infectious diseases spawned by filthy camp conditions. Over a period of four years, the Union states mobilized their superior assets and gradually wore down the South. As the war dragged on, it had the effect of radicalizing public opinion in the North. What began as a war to save the Union became a war against slavery. On January 1, 1863, Lincoln's Emancipation Proclamation made most of the nation's slaves "forever free" (see the box on p. 403). An increasingly effective Union blockade of the South combined with a shortage of fighting men made the Confederate cause desperate by the end of 1864

The final push of Union troops under General Ulysses S. Grant forced General Robert E Lee's Confederates to surrender on April 9, 1865 Although problems lay ahead, the Union victory confirmed that the United States would be "one nation, indivisible."

Between 1860 and World War I, the United States made the shift from an agrarian to a mighty industrial nation. American heavy industry stood unchallenged in 1900. In that year, the Carnegie Steel Company alone produced more steel than Great Britain's entire steel industry. Industrialization also led to urbanization. While established cities, such as New York, Philadelphia, and Boston, grew even larger, other moderate-size cities, such as Pittsburgh, grew by leaps and bounds because of industrialization. Whereas 20 percent of Americans lived in cities in 1860, more than 40 percent did in 1900.

By 1900, the United States had become the world's richest nation and greatest industrial power. Yet serious questions remained about the quality of American life. In 1890, the richest 9 percent of Americans owned an incredible 71 percent of all the wealth. Labor unrest over unsafe working conditions, strict work discipline, and periodical cycles of devastating unemployment led workers to organize. By the turn of the century, one national organization, the American Federation of Labor, emerged as labor's dominant voice. In 1900, however, it included only 8.4 percent of the American industrial labor force.