most ▁col ony ▁on ▁the ▁continent . ▁The ▁mission ▁system ▁arose ▁in ▁part ▁from ▁the ▁need ▁to ▁control ▁Spain ' s ▁ever - expand ing ▁hold ings ▁in ▁the ▁New ▁World . ▁Real izing ▁that ▁the ▁colon ies ▁required ▁a ▁liter ate ▁population ▁base ▁that ▁the ▁mother ▁country ▁could ▁not ▁supply , ▁the ▁Spanish ▁government ▁( with ▁the ▁co operation ▁of ▁the ▁Church ) ▁established ▁a ▁network ▁of ▁miss ions ▁to ▁convert ▁the ▁ind igen ous ▁population ▁to ▁Christian ity . ▁They ▁aim ed ▁to ▁make ▁converts ▁and ▁tax - pay ing ▁citizens ▁of ▁those ▁they ▁conquer ed . ▁To ▁make ▁them ▁into ▁Spanish ▁citizens ▁and ▁product ive ▁inhabitants , ▁the ▁Spanish ▁government ▁and ▁the ▁Church ▁required ▁the ▁ind igen ous ▁people ▁to ▁learn ▁Spanish ▁language ▁and ▁voc ational ▁skills ▁along ▁with ▁Christian ▁teach ings . ▁ ▁Est im ates ▁for ▁the ▁pre - contact ▁ind igen ous ▁population ▁in ▁California ▁are ▁based ▁on ▁a ▁number ▁of ▁different ▁sources ▁and ▁vary ▁substantial ly , ▁from ▁ 1 3 3 , 0 0 0 , ▁to ▁ 2 2 5 , 0 0 0 , ▁to ▁as ▁high ▁as ▁ 7 0 5 , 0 0 0 ▁from ▁more ▁than ▁ 1 0 0 ▁separate ▁tribes ▁or ▁nations . ▁ ▁On ▁January ▁ 2 9 , ▁ 1 7 6 7 , ▁Spain ' s ▁King ▁Charles ▁III ▁ordered ▁the ▁new ▁governor ▁Gas par ▁de ▁Port ol á ▁to ▁for ci b ly ▁exp el ▁the ▁Jes uits , ▁who ▁operated ▁under ▁the ▁authority