Basically when gold was discovered in California, it was acquired through a treaty that would end the ongoing war with Mexico in 1848. Waves of treasure hunters poured into the area. The California Gold Rush was a really big major factor in the process of expanding the West side of Mississippi.
The Westward Expansion was so greatly aided by it's completion of the Transcontinental Railroad in 1869, and the passage of the Homestead Act in 1862. Therefor that act was provided/given free 160-acre lots at the unsettled West, so whoever would file a claim, they would be living on that land for five years as well as deciding if they would want to make improvements to it. This would also include building a dwelling if wanted to.
I REALLY hope that this help's you out. I just learned about it so it should be right. Good Luck!