This chapter examines the Republic's expansion to the Pacific Ocean, its transformation into a continental nation, and the process by which these developments injected the slavery issue into national politics. It begins with the expansion of the Sioux onto the Plains, a reminder that westward expansion in American history involved more than Anglo-Saxon whites. Moreover, the case of the Sioux illustrates the importance of different kinds of frontiers in the process of expansion. Their conquest of the Plains ultimately depended on the acquisition of guns and horses, and the outbreak of disease epidemics that weakened enemy tribes and shifted the balance of power to the Sioux's favor. Along with the cultures of Indians, whites, and slaves, those of Hispanics in the Southwest and Chinese immigrants in the West combined to create diverse and often conflict-filled societies in the nation's newest territories.

Manifest (and Not So Manifest) Destiny

In the 1840s, American promoters proclaimed the United States' "Manifest Destiny" to expand across the North American continent. This doctrine combined idealistic motives with attitudes of racial superiority and a hunger for good farmland and harbors. Simultaneously, it also brought Americans into contact—and eventually conflict—with Mexicans in Texas, New Mexico, and California, all territories with relatively sparse populations that had existed under loose Mexican control since the Mexican Revolution of 1821.

Mexico initially welcomed American settlers into Texas in order to promote economic development in the region. Attracted by the promise of free land, Americans poured in, largely from the southern states, and soon became a clear majority of the population. Tensions with the Mexican authorities steadily mounted, and this friction eventually led to a revolution. In 1836 Texas forces defeated the Mexican army sent to quell the rebellion, and Texas became an independent republic. Americans in Texas hoped to annex themselves to the United States, but the Jackson and Van Buren administrations held back, fearful of stoking the fires of sectionalism.

The Trek West

Pushed by an extended economic depression in the East and lured by the promise of good land and a fresh start, other Americans headed for Oregon and California on the Overland Trail. Most migrants traveled in wagons as part of a family group. The journey, which took six months or more, put heavy pressures on families. Women on this journey often had to perform tasks normally reserved for men, and they complained about the breakdown of traditional gender roles on the trail as any semblance of a home, their traditional domain, disappeared.

Migration on the Overland Trail also took a heavy toll on the Plains Indians' way of life. Wagon trains scared off game and used up the grass and wood, which prompted the Sioux to demand payment for crossing their lands. Nevertheless, despite subsequent legends to the contrary, Indians actually attacked few trains along this route.

The Political Origins of Expansion

Politicians initially blocked the desire of the people of Texas to become part of the United States out of fears of raising the slavery issue, since Texas had legalized slavery. The death of the Whigs' first president, William Henry Harrison, only a month after he assumed office, however, brought John Tyler to the presidency. A proponent of states' rights, Tyler soon broke with the Whigs over economic policy. As a result, he took up the Texas issue in the hope of winning another term as president in 1844. This caused the Democratic Party to counter by dropping Martin Van Buren (who opposed the annexation of Texas) in favor of James K. Polk (who supported it) as the party's presidential candidate. Polk narrowly won the election over Henry Clay.

Polk entered the White House determined to expand American boundaries across the continent and to acquire the best harbors on the Pacific. He agreed to divide the Oregon territory with Britain, gaining the lower half, which included the desirable harbor of Puget Sound, for the United States. Upholding Tyler's annexation of Texas, he tried to buy New Mexico and California from Mexico, but when his diplomatic efforts failed he provoked a war with Mexico. Polk's willingness to use military means to achieve his goals provoked considerable opposition in American politics. The United States quickly conquered New Mexico and California, in part because Mexican forces were already weakened by extended Indian wars, and when Mexico stubbornly refused to make peace, American forces occupied Mexico City and forced Mexico to surrender. In the peace treaty, the U.S. acquired California and New Mexico, but northern Democrats, angry over Polk's pro-southern policies, injected the slavery issue into the controversy by introducing the Wilmot Proviso. The proviso sought to ban slavery from any territory gained from Mexico. Although it failed to pass the Senate, the Wilmot Proviso showed that the issue of slavery in the new territories had become an unavoidable and inflammatory political issue.

New Societies in the West

Overlanders sought to recreate in the West the societies they had left behind. With time, these communities became more stable and their economies more diversified, but wealth also became more concentrated and opportunity more constricted, just as it had in the East. The discovery of gold in California set off a frantic rush to the diggings in 1848. The gold rush created a unique society in the mining camps—one that was overwhelmingly male, strongly nativist, and without any sense of permanence. By 1852 miners had largely depleted the claims, and the remaining efforts became increasingly dominated by heavily capitalized corporations, whose mining procedures caused lasting environmental damage.

Cities also developed in the West. San Francisco, an "instant city" that sprung up in response to the gold rush, experienced rapid, chaotic growth. It was also an amazingly diverse community ethnically, with large numbers of Europeans, South Americans, Chinese, and other groups. Salt Lake City developed in a strikingly different way. In order to escape persecution for their unusual beliefs, including polygamy, the Mormons moved to the Salt Lake basin and established their own society in which they were free to worship as they chose. A planned community, Salt Lake City had an orderly appearance, since church officials carefully regulated its development.

The peace treaty with Mexico had incorporated a large number of Hispanics into the United States, but increasingly they came into conflict with the Anglo population, especially in Texas and California. Treated as inferiors, harassed, and often reduced to poverty, some expressed their frustration through social banditry.

Escape from Crisis

Solution of the territorial question became increasingly urgent in the wake of the 1848 California gold rush. As miners flocked to the region, California quickly garnered sufficient population to gain admission as a state. In addition, Mormons in the Salt Lake basin also asked for admission. Since neither state allowed slavery, the balance between slave and free states in Congress became threatened. When both major parties tried to avoid the issue of slavery's expansion in 1848, northern antislavery forces founded a new party, the Free Soil party, which urged adoption of the Wilmot Proviso. In a three-way race for president, Zachary Taylor, the Whig candidate who was a slaveholder and a hero of the Mexican War, won the election.

When Congress assembled in December 1849, the two sections remained locked in conflict, with many northerners calling for the prohibition of slavery in the Mexican cession and southerners demanding that the federal government open the area to slavery. Congress momentarily settled this question through the Compromise of 1850, a piece of legislation devised by Henry Clay and pushed through Congress by Stephen A. Douglas. The compromise settled the boundary dispute between Texas and New Mexico, included a new fugitive slave law, and adopted the principle of popular sovereignty (the people of the territory should decide) to deal with slavery in the Utah and New Mexico territories. Yet the Compromise was more an armistice than a compromise, since only one-fifth of the members had supported the entire Compromise.

Public opinion in both sections, however, rallied to the Compromise measures, and both the Whigs and the Democrats endorsed the Compromise in their 1852 platforms. Sectional harmony returned, and it seemed the Union had weathered the storm.