The National Park service offers a free annual pass to Active Duty Military Members and their Dependents. This pass allows the Military member and up to 3 adults (ages 16 & older; 15 and younger are free) within the same vehicle free admission to The Forest Service, the National Park Service, Fish and Wildlife Service, Bureau of Land Management, and Bureau of Reclamation sites where entrance or standard amenity fees are charged. This pass, however, does not cover expanded amenity fees such as camping, boat launch or interpretive fees.
Military members will need to present their CAC card at one of the Federal lands that charge an entrance fee in order to obtain the annual pass. Those that have sponsors deployed just need to present DOD form 1173.
It’s best to call beforehand to make sure they have these special passes available.
For more information see the Overview of the Annual Pass for Active Duty Military and Their Dependents page at the U.S. Geological Survey’s website..