sentences:  Placer gold deposits were found at San Ysidro in San Diego County in 1828, San Francisquito Canyon and Placerita Canyon in Los Angeles County in 1835 and 1842, respectively
  
  Major gold mining in California began during the California Gold Rush.Gold was found by James Marshall at Sutters Mill, property of John Sutter, in present-day Coloma.In 1849, people started hearing about the gold and after just a few years San Francisco's population increased to thousands.