By 1800, both the United States and Great Britain had a foothold in the Oregon Country. This area includes present-day Oregon, Washington, Idaho, and parts of Wyoming and Montana. The Lewis and Clark expedition, fur traders, missionaries, and early settlers strengthened United States claims to Oregon. In 1848, the United States annexed Oregon in a peaceful border settlement with Britain.
While wagon trains rolled along the Oregon Trail in the north, other American settlers headed into Texas. Stephen F. Austin, under a grant from the Mexican government, founded the first and most successful colony in 1825. Disagreements over slavery and Mexican laws led Texans to declare independence from Mexico in 1836. By this time, the spirit of Manifest Destiny had overtaken the country, and many Americans wanted to annex Texas. Annexation took place in 1844.
Two years later, the United States declared war against Mexico and defeated its neighbor to the south. Under the 1848 Treaty of Guadalupe Hidalgo, the United States acquired the Mexican Cession. This territory takes in present-day California, Nevada, Utah, and parts of Arizona, Colorado, Wyoming, and New Mexico. The nation now stretched from sea to sea.
Mormon settlers, arriving in 1847, had already started an American settlement in Utah. News of gold found in California brought a rush of settlers to the territory in 1849. In 1850, California became a state.
