Final answer:
The discovery of gold prompted many people to move to California in 1848.
Step-by-step explanation:
The event that prompted many people to move to California in 1848 was the discovery of gold. In January 1848, gold was found at John Sutter's sawmill in northern California. This discovery led to a surge in population as people from different parts of the country and even from other countries rushed to California in search of gold and fortune.