Final answer:
By the mid-1850s, most of California's surface gold was depleted, and independent miners were giving way to large companies. This transition in the mining industry led to the development of larger businesses and greater urban stability.
Step-by-step explanation:
By the mid-1850s, most of California's surface gold was gone, and the independent miner was being replaced by large mining companies. Independent miners were supplanted by companies that could afford not only to purchase hydraulic mining technology but also to hire laborers to work the hills. This shift led to larger businesses underwriting mining operations, which eventually led to the development of greater urban stability and infrastructure.