▁first ▁of ▁several ▁subsequent ▁exped itions ▁into ▁the ▁Central ▁Valley , ▁in ▁order ▁to ▁find ▁potential ▁mission ▁sites . ▁Mor aga ▁started ▁out ▁from ▁Mission ▁San ▁Juan ▁B aut ista , ▁in ▁present - day ▁San ▁Ben ito ▁County , ▁on ▁September ▁ 2 1 ▁of ▁that ▁year ▁and ▁tra ve led ▁east ▁into ▁the ▁San ▁Jo aqu in ▁Valley . ▁The ▁group ▁sk irt ed ▁the ▁western ▁fo oth ills ▁of ▁the ▁Sierra ▁and ▁christ ened ▁many ▁place ▁names ▁that ▁remain ▁in ▁use ▁today . ▁In ▁ 1 8 0 7 ▁and ▁ 1 8 0 8 , ▁Mor aga ▁set ▁out ▁again ▁to ▁the ▁San ▁Jo aqu in ▁Valley . ▁It ▁was ▁during ▁one ▁of ▁these ▁exped itions ▁that ▁he ▁gave ▁the ▁river ▁its ▁present ▁name , ▁after ▁St . ▁Jo achim . ▁He ▁also ▁gave ▁names ▁to ▁many ▁trib ut aries ▁of ▁the ▁river , ▁such ▁as ▁the ▁Mer ced ▁River ▁( El ▁Río ▁de ▁Nu estra ▁Se ñ ora ▁de ▁Mer ced , ▁" R iver ▁of ▁our ▁Lady ▁of ▁Mer cy "). ▁ ▁Although ▁relations ▁between ▁the ▁Spanish ▁and ▁the ▁Native ▁Americans ▁in ▁the ▁earlier ▁exped itions ▁to ▁the ▁valley ▁were ▁initially ▁friendly , ▁the ▁ind igen ous ▁people ▁began ▁to ▁grow ▁acc ustom ed ▁to ▁the ▁Spanish ▁that ▁later ▁came ▁to ▁the ▁San ▁Jo aqu in ▁River ▁region . ▁As ▁early ▁as ▁the ▁ 1 8 0 7 ▁Mor aga ▁expedition , ▁it ▁was ▁reported ▁that ▁some ▁n atives ▁were ▁host ile ▁and ▁attempting ▁to ▁ste al