The county-designated highways in Michigan' comprise a 1,241.6-mile-long (1,998.2 km) system of primary county roads across the US state of Michigan. Unlike the State Trunkline Highway System, these highways have alphanumeric designations with letters that correspond to one of eight lettered zones in the state. The County-Designated Highway System (CDH System) was created in 1970 in response to the business concerns of a woman f
rom Saugatuck. Her one-woman crusade in the 1960s started after the highway in front of her motel was turned over to local control as a county road and removed from state highway maps when the nearby freeway opened. After nearly a decade of efforts, the first two test highways were designated, one each in the Lower and Upper peninsulas of the state and included on the 1970 state highway map. The system was created and expanded in scope c. October 5, 1970, after it was approved by the County Road Association of Michigan and the State Highway Commission.
The system uses eight lettered zones which are divided by major state highways. Each county road in the system is designated with the zone letter followed by a number. Six of the zones, A–F, are in the Lower Peninsula while the Upper Peninsula is divided into the remaining two, G and H. There have been a total of 66 different highways designated in seven of the zones; as of 2021 no E highways have been named. Participation by the county road commissions is optional, and not all counties use the system. One additional highway, Forest Highway 16 (marked as "H-16"), has appeared on state maps since the 1980s although it is not a part of the system. Of the highways designated, two were removed from the system and later partially restored.
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