 In 1928 , the first M @-@ 108 designation was commissioned along a rare three @-@ legged route connecting the State Highway Ferry Docks with the Fort <unk> State Historic Park and US 31 . At one point while traveling westbound on M @-@ 108 , motorists could turn right onto northbound M @-@ 108 or left onto southbound M @-@ 108 . In preparation for the opening of the Mackinac Bridge , the Michigan State Highway Department transferred all of M @-@ 108 to local control in late 1957 , decommissioning the designation at the same time . In 1960 , the current M @-@ 108 was commissioned along the current routing . 
