 When US @-@ 89 was created in 1926 , it only went as far north as Spanish Fork , where travelers could continue to Salt Lake City via US @-@ 91 . The highway was extended north to the Canada – US border near Glacier National Park in the mid @-@ 1930s , though a dispute between Utah and Idaho on the one side and Wyoming on the other was not settled until 1938 . The American Association of State Highway Officials decided in favor of Utah and Idaho , placing US @-@ 89 on or near US @-@ 91 between Spanish Fork and Logan , where it split northeasterly to Yellowstone National Park . ( US @-@ 89 only left US @-@ 91 twice : between Farmington and Ogden , where it still travels today , and via an all @-@ weather route from Brigham City into the Cache Valley , now SR @-@ 38 and SR @-@ 30 . ) Wyoming 's preferred routing , which left US @-@ 91 at Provo , instead became US @-@ 189 . Beginning in the 1950s , Interstate 15 was constructed , replacing US @-@ 91 for through traffic south of Brigham City , and leading to that route 's truncation there in 1974 . On the other hand , US @-@ 89 follows independent corridors south of Spanish Fork and north of Logan . It has not been truncated , and mostly follows US @-@ 91 's final alignment , except between Farmington and Ogden ( where old US @-@ 91 is now I @-@ 15 , SR @-@ 126 , and SR @-@ 26 ) . 
