Final answer:
San Francisco was the city in California that experienced a boom during the gold rush.
Step-by-step explanation:
The city in California which saw a boom during the gold rush was San Francisco. During the mid-1800s, the discovery of gold in California attracted a rush of people to San Francisco in search of riches. The city experienced rapid growth and development as a result of the gold rush, becoming an important center for trade and commerce.
Learn more about Gold rush in California