<P> The first quarter of the 19th century showed the continuation of the slow colonization of the southern and central California coast by Spanish missionaries , ranchers and troops . By 1820 Spanish influence was marked by the chain of missions reaching from Loreto , north to San Diego , to just north of today 's San Francisco Bay Area , and extended inland approximately 25 to 50 miles ( 40 to 80 km ) from the missions . Outside of this zone , perhaps 200,000 to 250,000 Native Americans were continuing to lead traditional lives . The Adams -- Onís Treaty , signed in 1819 , set the northern boundary of the Spanish claims at the 42nd parallel , effectively creating today 's northern boundary between California and Oregon . </P>
in the early 1800s california society was dominated by which group
Spanish