U.S. Wins ‘Upper California’

In February 1848, the Mexican-American War ended with the Treaty of Guadalupe Hidalgo, which officially awarded America the territory of Upper California.
The area was known (or rather, unknown) for being rural and isolated. But, thanks to one man’s discovery, those days were numbered.
The above photo shows the harbor of San Francisco during the California Gold Rush, when the city’s population was around 25,000.