The cause of the gold rush was the discovery of gold in California in 1848. What was an effect of the gold rush? Thousands of settlers moved west, leading to the growth of cities like San Francisco. Thousands of Native Americans started business based on gold and became rich. Some farmers started trading their bushels of corn for baskets of tomatoes as part of a barter system. Societies in China, South Asia and parts of Africa started using shells as a form of money.