Senior pass

[popeyemth]

Mammoth Cave National Park is out of senior passes
They will issue a "rain check "
You have to physically apply and physically return to pick up

[SAR_Tracker]

Many locations are "out" of the passes, so it IS easiest to get one by mail. I had to call around and finally found a USFS station that had some.

[Corkey05]

Or go HERE and let the postman do the walking.

I've been hearing reports of Parks running out of passes, so if you're not in a hurry online might work for you.