Explain that at the end of the Mexican-American war, the United States gained control of Mexican territories in the West, which included present-day California. Americans slowly began settling there, until the discovery of gold brought quick population growth and an economic boom. Students will be asked to discuss the following questions before beginning the lesson: What types of people do you believe participated in the California gold rush, and how did they take part in it? What possible problems do you think can arise by the arrival of so many new settlers in California? Ask students if they would travel west to seek fortune in California.