You will find parks like that, mostly ownership or membership, in the upper part of the lower peninsula of Michigan. Spaces are sometimes open for rental when a site owner decides not to return to Michigan during the summer.
Here too, as in the mountain West, summer is peak season and demandi is high, traffic coming from midwest industrial cities. Upper LP is summer destination for the wealthy of Detroit and Chicago, tradition going back to late 19th century when they got up there by train and boat.