Final answer:
The Gold Rush was responsible for the increase in California's population and its statehood.
Step-by-step explanation:
The event responsible for the increase in California's population and its statehood was The Gold Rush.
In 1848, gold was discovered at Sutter's Mill, sparking a frenzy of people from around the world to migrate to California in search of fortune.
As the population grew rapidly, California was able to achieve statehood in 1850, just two years after the gold discovery.
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