 When US @-@ 89 was established in the state in 1926 , the road initially extended north to US @-@ 91 in Spanish Fork . Following the extension of the former to the Canada – US border , Interstate 15 was constructed roughly paralleling US @-@ 89 to the west and replacing US @-@ 91 south of Brigham City . During this process , US @-@ 89 was rerouted in southern Utah and northern Arizona with the old roadway becoming US @-@ 89A . 
