▁toward ▁the ▁head w aters ▁of ▁the ▁Missouri , ▁int ending ▁to ▁locate ▁the ▁source ▁of ▁the ▁Y ellow stone ▁River ▁and ▁explore ▁it ▁until ▁its ▁confl u ence ▁with ▁the ▁Missouri . ▁Lewis ' ▁group ▁did ▁not ▁visit ▁Tower ▁Rock . ▁The ▁main ▁party ▁under ▁Clark ▁followed ▁the ▁B itter root ▁River ▁south ▁to ▁S ula , ▁Mont ana , ▁where ▁it ▁turned ▁south ▁toward ▁Gib b ons ▁Pass ▁and ▁the ▁crossing ▁of ▁the ▁Cont inental ▁Div ide . ▁Following ▁a ▁series ▁of ▁cre eks ▁and ▁tra ils ▁south west ward , ▁Clark s ' ▁party ▁reached ▁the ▁Big ▁H ole ▁River , ▁following ▁it ▁to ▁the ▁Jefferson ▁River ▁and ▁then ▁to ▁the ▁Missouri ▁again . ▁At ▁Three ▁F ork s ▁( where ▁the ▁Jefferson , ▁Gall atin , ▁and ▁Mad ison ▁rivers ▁join ▁to ▁form ▁the ▁Missouri ▁River ), ▁on ▁July ▁ 1 3 , ▁ 1 8 0 6 , ▁Clark ▁ordered ▁Serge ant ▁John ▁Ord way ▁to ▁take ▁a ▁group ▁of ▁nine ▁and ▁go ▁down ▁the ▁Missouri ▁to ▁the ▁camp ▁at ▁White ▁Bear ▁Island ▁and ▁there ▁await ▁Mer iw ether ▁Lewis . ▁On ▁the ▁afternoon ▁of ▁July ▁ 1 7 , ▁the ▁Ord way ▁party ▁approached ▁Tower ▁Rock . ▁But ▁high ▁wind s ▁came ▁up , ▁causing ▁heavy ▁waves ▁which ▁nearly ▁sw amp ed ▁the ▁can o es . ▁The ▁Ord way ▁group ▁was ▁forced ▁to ▁spend ▁the ▁afternoon ▁and ▁night ▁near ▁Tower ▁Rock ▁before ▁proceed ing ▁past ▁Half - Bre ed ▁Rap ids ▁the ▁next ▁day . ▁Ord