On May 13, 1913, the Legislature created the state's highway system; Woodward Avenue was included as part of "Division 2". The full length was paved in 1916. The first crows nest traffic tower in the US was installed at the intersection of Woodward and Michigan avenues on October 9, 1917; the tower elevated a police officer above the center of the intersection to direct traffic before the structure was replaced in October 1920 with the world's first four-way traffic light. The state signposted its highways in 1919, and Woodward Avenue was assigned the M-10 designation. The same year, two auto trail designations were applied to the avenue. The Theodore Roosevelt International Highway was created in February 1919, running from Detroit northward along Woodward Avenue. Later that year, the Dixie Highway was extended through Detroit to the Straits of Mackinac, following the route of the old Saginaw Trail northward along Woodward Avenue.