Correct Response: A. Following the discovery of gold in California during the late 1840s, people from all regions of the country flocked to the territory, substantially increasing its population. A transcontinental railroad (B) that linked California to eastern regions of the country did not open for through traffic until 1869, and most of the U.S. soldiers who fought in the Far West during the Mexican War (C) returned home afterward. While Chinese immigrants to California were also lured by the reports of gold (D), their numbers formed only a small part of the increase in San Francisco's population during the late 1840s.
