My wife got her senior citizen federal pass a couple years ago. We were visiting the sand dunes in Michigan. It cost $10.00 I think. When we were visiting Yellowstone we only had to show her federal pass and driver's license to get in free, while others paid well over $20.00.
I think we have only used it one other time but it was well worth the $10.00 investment.
2014 Montana 3725RL (Goodyear G614 Tires, Flow Thru TPMS)
SPENDING THE WINTERS AT OUR HOME IN SW FLORIDA. THE REST OF THE YEAR SEEING THE U.S. FROM OUR LIVING ROOM WINDOW!