With the coming of the Interstate Highway System in Michigan , the MSHD planned to convert the eastern section of US 2 to a freeway between St. Ignace and Sault St. Marie . In planning maps from 1947 , this highway corridor was included in the system that later became the Interstates . It was also included in the General Location of National System of Interstate Highways Including All Additional Routes at Urban Areas Designated in September 1955 , or Yellow Book after the cover color , that was released in 1955 as the federal government readied plans for the freeway system . The proposed number in 1958 was Interstate 75 ( I ‑ 75 ) .