▁the ▁San ▁Jo aqu in ▁was ▁Rio ▁de ▁San ▁Francisco , ▁which ▁was ▁the ▁name ▁Father ▁Juan ▁C resp í ▁gave ▁to ▁the ▁river ▁he ▁could ▁see ▁entering ▁the ▁Sac r amento - San ▁Jo aqu in ▁D elta ▁from ▁the ▁south . ▁A ▁member ▁of ▁the ▁Pedro ▁F ages ▁party ▁in ▁ 1 7 7 2 , ▁C res pi ' s ▁v antage ▁point ▁was ▁the ▁hill top s ▁behind ▁modern ▁Ant io ch . ▁Another ▁early ▁name ▁was ▁Rio ▁San ▁Juan ▁B aut ista , ▁the ▁origin ▁of ▁which ▁is ▁unknown . ▁ ▁Cour se ▁ ▁The ▁river ' s ▁source ▁is ▁located ▁in ▁the ▁An sel ▁Adams ▁W ilder ness , ▁in ▁the ▁south - central ▁Sierra ▁Nev ada ▁at ▁the ▁confl u ence ▁of ▁three ▁major ▁aff lu ents : ▁the ▁Middle ▁F ork , ▁which ▁r ises ▁from ▁Th ous and ▁Island ▁Lake ▁at ▁almost ▁ ▁above ▁sea ▁level , ▁ ▁the ▁North ▁F ork , ▁which ▁starts ▁ ▁sout heast ▁of ▁Mount ▁Ly ell , ▁ ▁and ▁the ▁South ▁F ork , ▁which ▁begins ▁at ▁Mar tha ▁Lake ▁in ▁Kings ▁C any on ▁National ▁Park ▁and ▁flows ▁through ▁Florence ▁Lake , ▁joins ▁a ▁short ▁distance ▁down stream . ▁The ▁Middle ▁F ork ▁is ▁considered ▁the ▁largest ▁of ▁the ▁ 3 ▁for ks . ▁From ▁the ▁mountain ous ▁al pine ▁head w aters , ▁the ▁San ▁Jo aqu in ▁flows ▁generally ▁south ▁into ▁the ▁fo oth ills ▁of ▁the ▁Sierra , ▁passing ▁through ▁four ▁hydro elect ric