Most people go to Wilderness State park on the south side of the bridge, but this is an equally wonderful campground.  As with Wilderness, this park has two sections of campgrounds- a higher loop in the woods and a lower loop along the shore of Lake Michigan.  Both are desirable and have decent sized sites.  There is a good hiking trial through the park with multiple vista points for viewing the lake and Mackinac Bridge.  It's a couple minutes away from the ferry to go to Mackinac Island.  Highly recommend this campground particularly when other ones are harder to get into.