▁to ▁connect ▁the ▁bur geon ing ▁min ing ▁district ▁around ▁But te , ▁Mont ana , ▁with ▁Hel ena ▁and ▁the ▁nas cent ▁city ▁of ▁Great ▁F alls . ▁Survey ors ▁and ▁engine ers ▁began ▁grad ing ▁a ▁route ▁between ▁Hel ena ▁and ▁Great ▁F alls ▁through ▁the ▁Missouri ▁River ▁can y on ▁in ▁the ▁winter ▁of ▁ 1 8 8 5 - 1 8 8 6 , ▁and ▁by ▁the ▁end ▁of ▁ 1 8 8 6 ▁had ▁survey ed ▁a ▁route ▁from ▁Hel ena ▁to ▁But te . ▁Const ruction ▁on ▁the ▁Great ▁Northern ' s ▁line ▁west ward ▁began ▁in ▁late ▁ 1 8 8 6 , ▁The ▁rail road ▁line ▁passed ▁between ▁Tower ▁Rock ▁and ▁the ▁river , ▁forcing ▁the ▁construction ▁cre ws ▁to ▁do ▁some ▁bl ast ing ▁to ▁clear ▁room ▁at ▁the ▁extreme ▁edge ▁of ▁the ▁land mark ' s ▁base . ▁On ▁October ▁ 1 6 , ▁ 1 8 8 7 , ▁the ▁link ▁between ▁Dev ils ▁Lake , ▁North ▁Dak ota ; ▁Fort ▁Ass inn ib o ine ▁( near ▁the ▁present - day ▁city ▁of ▁Hav re ); ▁and ▁Great ▁F alls ▁was ▁complete . ▁Service ▁from ▁Great ▁F alls ▁to ▁Hel ena ▁began ▁in ▁November ▁ 1 8 8 7 , ▁and ▁But te ▁followed ▁on ▁November ▁ 1 0 , ▁ 1 8 8 8 . ▁ ▁The ▁un in cor por ated ▁ham let ▁of ▁Hard y ▁was ▁established ▁on ▁the ▁north ▁boundary ▁of ▁Tower ▁Rock ▁as ▁a ▁s iding