In a similar vein, the state parks of Minnesota usually charge a fee for parking and sometimes for entrance, but those fees are waived on Black Friday. I call it State Park Friday and my wife and I go for a short hike every year :)
State Park passes are cheap enough in MN. If you enjoy them consider an annual pass to support the DNR and enjoy the parks year round!
I wish they would just wrap a state park pass up with the conservation plates...