At entrance. Or secretary of state.
Window and attendant at park entrance.
If it is the park pass you can get it when you renew license plates in Michigan as well. Then it is on your tab.
Need to purchase a state of Michigan yearly permit. $16.00. they sell at entrance to park. Good at all State Park
They offer a variety of park pass options during normal business hours at the entry booth, they even take debit card if memory serves.
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