If you are 62 or over and don't have a national parks senior pass, you should consider getting one.
It costs $10 and is good for your lifetime and allows you and up to three other adults (children under 16 always free) in your vehicle into national parks for free.
The price is going up to $80 sometime this year. A friend told me the hike will be beginning in July, but what I could find online just says sometime in 2017.
Here's a link to what it does: About the Senior Pass
Here's a list of sites that issue the pass for $10.00.
If you don't want to go out to get it, you can order it online at the usgs.gov store for $20.00 ($15.00 for the packet and $5.00 shipping).
You have to provide ID that you are 62 or over. You can upload a copy of your passport or driver's license on a link they provide.