Many settlers traveled west in large groups of wagons called wagon trains. They headed west for different reasons, some searching for cheap land, some hoping to find gold or silver, some looking for religious freedom. More than 300,000 people took the Oregon Trail to the Oregon Territory, and others took the Santa Fe Trail that led to Los Angeles.

Some of the early westward travelers included the missionaries Marcus and Narcissa Whitman, who set up a mission near the Columbia River in the Oregon Territory. In 1847, Brigham Young led over 14,000 mormons on the Mormon Trail to present-day Utah in search of religious freedom. Fur trappers like Jim Bridger and James Beckwourth, who was a runaway slave, were known as Mountain Men because they knew the mountains and trails so well.

The discovery of gold in 1848 by James Marshall at Sutter's Mill led to the beginning of the Gold Rush. Thousands of people raced along the California Trail to be a part of it. Many miners arrived in California in 1849 and became known as the forty- niners. At that time, California had outlawed slavery and allowed married women to own property. With its population growing rapidly, California became a state in 1850.