 In 1957 , one year after construction began on the Glen Canyon Dam , the legislature designated a new State Route 259 , heading east and southeast from SR @-@ 11 in Kanab to Arizona en route to the dam and adjacent bridge . This replaced about eight miles ( 13 km ) of SR @-@ 136 ( the original state highway from the 1910s ) at its south end , but the remainder was a new roadway , through an area not previously served by improved roads . The route past the dam was initially designated as an alternate route of US @-@ 89 , but when completed on February 20 , 1959 it instead became US @-@ 89 's mainline , as it was a better route during all weather , and the old route ( SR @-@ 11 south of Kanab ) became U.S. Route 89 Alternate . 
