In 1929, this version of M-64 was renumbered M-9. In 1934, M-9 traveled on Pioneer Road in Hillsdale County, from the Ohio border before turning west on Burt Road, north on Clark Road, west on Montgomery Road then north onto Hillsdale Road. During this time a loop was planned to continue north from the corner of Pioneer and Burt Roads to Montgomery Road where it turned west and met with M-9 at Clark Road. This short loop was designated M-158, however later in the year the routing of M-9 was shifted onto the M-158 alignment, eliminating that route. By the middle of 1936, the highway was extended northward to end in Lansing. The M-9 designation was replaced with M-99 in 1940.