Stone age man settled down in California over 10,000 years ago, beginning a population expansion that lasts to this day (and beyond). over 70 different native American tribes called California their home up through the 1800's (and beyond, but not in the same numbers). Spanish missionaries traveled up the California coast from Mexico around the turn of the 18th century, settling 23 missions in various strategic spots near large concentrations of Native Americans. The intent was to bring structure (and Catholicism) to the natives. Fur trappers settled in the hills of California in the early 1800's and of course the California Gold Rush of the 1840's-1850's happened, resulting in the non-native population of California to boom from 15,000 to 300,000 virtually overnight.