according to u.s news and world report,
the national park service offers a whopping senior discount on their
park passes for folks over age 62 ... instead of the normal $80/year,
it's $10 and never expires!

sure enough ...
http://www.nps.gov/vama/planyourvisit/interagency-senior-pass.htm
ah, but it's an interagency senior pass ...
gets you into not just the national park service, but also BLM, Corps
of engineers, fish and wildlife, forest service, and TVA sites with
entrance fees.

pass admits pass holder and passengers in non-commercial vehicle at
per vehicle fee areas, and pass holder + 3 adults at per person fee
areas (kids under 16 are not adults and are admitted free).

available only in person at most BLM, NPS, FWS, FS, or TVA watershed
team offices. proof of age must be shown.

unca joel