Answer:
The population of San Francisco, California, skyrocketed around 1850 because of the discovery of gold in the Sierra Nevada.
Step-by-step explanation:
The city was founded in 1776 by Spanish settlers. Following independence from Spain, the area became part of Mexico.
The city, like the rest of the territory of present-day California, was torn by the United States from Mexico following the Mexican-American war (1846-1848), and was renamed San Francisco. It was the Californian gold rush that followed the American annexation that stimulated a rapid growth of the area, and its definitive transformation from a small urban center into a big city: from 1000 inhabitants in 1848 it passed to 25000 in December 1849. New demographic impulse gave the discovery of silver mines in 1859; this uncontrolled growth also caused a greater incidence of crime in the city, and some neighborhoods became known as a paradise for criminals, prostitution and gambling.